HVAC shee v10

Flame rectification

120v is supplied to the flame rod. When a flame is present the voltage will pass through the ionized flame and onto the ground strap. This DC voltage will then pass through a dedicated wire that is attached to the ground strap and back to the control board to signal that a flame is present.

oz to lb

16 oz = 1 lb 1 oz = 28.34 grams a pint weighs 16 ounces

usb voltage

5 volts DC

purpose of blower door test

A blower door is a machine used to measure the airtightness of buildings. It can also be used to measure airflow between building zones, to test ductwork airtightness and to help physically locate air leakage sites in the building envelope. The blower door test costs about $450 for a typical house. A blower door is a powerful fan that mounts into the frame of an exterior door. The fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed cracks and openings. The auditors may use a smoke pencil to detect air leaks.

Braking resistor

A braking resistor helps to slow down or stop a motor by dissipating excess voltage generated by the decelerating motor. When power is removed from a motor, the load is reduced causing it to turn at a faster rate. The motor acts as a generator, creating electrical energy which flows back into the power circuit.

passive sensor

A passive sensor is a device that detects and responds to some type of input from the physical environment. Passive sensor technologies gather target data through the detection of vibrations, light, radiation, heat or other phenomena occurring in the subject's environment. e.g. CAD cell, pressure switch, temp sensor

Integrated Circuit (IC)

A thin slice of silicon that contains many solid-state components. An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material that is normally silicon. The integration of large numbers of tiny MOS transistors into a small chip results in circuits that are orders of magnitude smaller, faster, and less expensive than those constructed of discrete electronic components. The IC's mass production capability, reliability, and building-block approach to circuit design has ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs.

Transcritical cycle

A transcritical cycle is a thermodynamic cycle where the working fluid goes through both Subcritical and supercritical states. This is often the case when carbon dioxide, CO2, is the refrigerant.

mixed air sensor

A true mixed air sensor would be installed where the RA and OA mix, before the cooling coil. With the advent of smashing economizers into RTUs and the use of modules things were simplified and the discharge and mixed air were combined into one

How to convert AC to DC mathmatically

AC voltage * √2 e.g. 480V AC system DC equivalent would be: 480 * √2 = 679V DC

who made the electric refrigerator?

According to a paper published by Wright State University, Fred W. Wolf invented the first commercially viable electric refrigerator in the United States. Sold for the first time in 1913, the DOMELRE, an air-cooled refrigeration unit, was mounted on top of an icebox

Using Compression to Dry Air

As air is compressed, the dew point or temperature at which water will condense is raised. Therefore, to get dry air we need to find a way to cool the compressed air. But costs can be prohibitive because equipment, space, and auxiliary equipment are necessary for the process. However, if compressed air is already used in the primary operation and only very small amounts of dry air are needed for humidity control, compression may be a feasible route to dry air. When air at extremely high pressure (over 200 lbs/sq in) is needed, small quantities of high pressure air may be used to maintain small enclosures at the required moisture level. It is also possible to use small amounts of the high pressure air with a smaller air facility to control moisture on a limited scale.

frequency impact on heat

As the frequency goes up, heat generation goes up. Heat is the enemy of any electronic system.

Why do welding flames form distinct cone layers? Shouldn't the layers just be gradiented together?

As the fuel burns out, it goes through the phases of ignition, superficial oxidation, free radical branching, formation of carbon monoxide, carbon formation, total oxidation to carbon monoxide, and final burnout. There is not a smooth gradient. The layers you see correspond to different temperatures as the fuel molecules go through these phases. The fuel/oxidant ratio determines the phase and color of the different layers.

How do carbon monoxide sensors work?

Biomimetic sensor: a gel changes color when it absorbs carbon monoxide, and this color change triggers the alarm. Metal oxide semiconductor: When the silica chip's circuitry detects carbon monoxide, it lowers the electrical resistance, and this change triggers the alarm. Electrochemical sensor: Electrodes immersed in a chemical solution sense changes in electrical currents when they come into contact with carbon monoxide, and this change triggers the alarm. Previously CO sensors used in many home alarms were biomimetic: they imitate human biology in that an enzyme gel inside the sensor darkens as more CO is absorbed. They absorb and release CO in a pattern similar to human physiology. The change in translucency of the gel is sensed with light. The change in light is proportional to CO concentration in the air.

Gas cooler

CO2 gas coolers replace traditional air-cooled condensers in refrigerating systems designed for the use of carbon dioxide as a single refrigerant. In a gas cooler, hot compressed CO2 gas flows through the cooler tubes and is cooled down by the ambient air that is forced through the coil. Due to CO2 being transcritical, it will not condense like standard refrigerant.

R-454b

Carrier has adopted the Chemours refrigerant R454B as its primary lower GWP replacement for R410A in ducted residential and light commercial air conditioners sold in North America. R454B is a "mildly flammable" A2L refrigerant blend of 68.9% R32 and 31.1% 1234yf. It has a GWP of 466. Sold by Chemours as Opteon XL41, but to be commercially renamed by Carrier as Puron Advance, the new refrigerant will be offered in Carrier products from 2023.

compression fitting

Compression fittings are used in plumbing and electrical conduit systems to join two tubes or thin-walled pipes together. In instances where two pipes made of dissimilar materials are to be joined, the fittings will be made of one or more compatible materials appropriate for the connection.

Sequence of operation - gas furnaces

- Heat call from the thermostat. - Control board does a safety check (limit switches, roll out switches). - Inducer motor comes on. - Pressure switch must close to go to the next step. - Hot surface ignitor begins getting hot / direct spark ignitor begins to spark - Gas Valve opens - Furnace Lights - Flame Sensor senses flame - 30 seconds - 1 minute blower motor comes on. - Once thermostat is satisfied, the burner shuts off

CO2 Saturation Table

Critical point - the critical point of CO2 is 1070 psia (1055.3 psig) and 87.8°F. This is highest pressure and temperature where liquid and gas can exist simultaneously. The region above this point is considered supercritical, below this point is subcritical. NOTE: NEVER ALLOW LIQUID CO2 TO BECOME TRAPPED IN THE SYSTEM WITHOUT MEANS FOR PRESSURE RELIEF, THIS CAN BE EXTREMELY DANGEROUS! https://www.hussmann.com/ns/Technical-Documents/CO2_Transcritical_Systems_Training_Manual_042718.pdf

what does the pint rating on a dehumidifier mean?

Dehumidifier capacity is rated by the amount of moisture removed in 24 hours, so a 30-pint dehumidifier is rated to remove 30 pints of moisture in one day. One pint is one pound of water so you remove 30 lbs of water per day.

Difference between subcritical refrigerants and transcritical refrigerants

Figure 2 is a pressure-enthalpy diagram for R-134a in a traditional vapor compression refrigeration cycle. Starting at the lower left of the figure and moving to the right, the bottom line represents the evaporation process. Refrigerant pressure (the y axis) remains constant in the evaporator, and heat gain during the evaporation process is represented by the increasing specific enthalpy (which can be interpreted as specific "energy content" of the refrigerant, measured along the x axis). On the right side of the figure, the line slanting upward to the right as pressure rises sharply and steadily is the compression process, where we add power to the system to run the compressor. In the top horizontal line of the figure, moving from right to left, the condensing process occurs. Here the heat absorbed during evaporation - and the heat added during compression - is rejected out of the system. During the condensing process, the quality of the refrigerant changes until it is 100 percent liquid. A further cooling of the liquid often occurs so that the refrigerant is subcooled when leaving the condenser. There is no change in pressure or temperature during the phase change. The final process in the cycle is expansion, represented by the drop in refrigerant pressure along the left side of the figure. The pressure drop occurs as the refrigerant passes through a metering device (expansion valve or capillary tube). During the expansion process, refrigerant condition changes from subcooled liquid to a mixture of liquid and vapor. No heat or work is transferred to or from the refrigerant during this process, so the line representing the process is vertical. There is no change in specific enthalpy. So in the cycle for R-134a, and for other subcritical refrigeration cycles, the four processes are evaporation, compression, condensation, and expansion. Note that the entire cycle takes place below the green dot at the critical point. Things are just a bit different in transcritical cycles. Figure 3 represents a transcritical cycle with CO2. The cycle diagram looks the same; the only difference is that the heat rejection process occurs above the critical point. Unlike the subcritical condensing process, where temperature stays constant, temperature decreases during the entire transcritical heat rejection process. There is no condensation in a transcritical cycle, and we call the process gas cooling. In low ambient conditions, the process might occur below the critical point, and condensation, rather than gas cooling, would occur. This is the fundamental difference between subcritical and transcritical cycles. A system based on the transcritical CO2 cycle uses a high pressure expansion valve (HPEV). Rather than controlling refrigerant metering from the low-pressure side of the system, modulation control comes from the high side of the system. A mechanical HPEV will control refrigerant injection into the evaporator by opening and closing based on the increase or decrease in gas cooler pressure. In the HPEV, spring force is a closing force that acts on the top of a diaphragm. Increasing spring force throttles the valve, causing a backpressure in the gas cooler; the valve will not open until that back pressure, opposing spring force, increases to the point where it can overcome spring force and open the valve. The valve set point for the inlet pressure can be adjusted manually by compressing a spring in the valve. Unlike a TEV, an HPEV does not control evaporator superheat. The HPEV injects refrigerant into the evaporator, but superheat is not directly controlled - instead it is indirectly regulated by system design. The system charge, its distribution between the components, evaporator design, and the heat load, along with other external operating conditions, determines system superheat. By controlling the gas cooler pressure, the HPEV will indirectly influence system superheat, but the system must be designed so that liquid refrigerant in the evaporator outlet is not allowed to return to the compressor. The HPEV was designed to control gas cooler pressure rather than suction line superheat as does a TEV. An HPEV, therefore, must withstand high-side CO2 pressures that can reach 1500 psia, at the same time accurately controlling gas cooler pressure. Slight changes in gas cooler pressure will have significant influence on the system cooling capacity and energy efficiency (COP). https://www.achrnews.com/articles/94092-co2-as-refrigerant-the-transcritical-cycle

What is the difference between dry contact and wet contact?

From a controls standpoint, when a device calls for a "dry" contact, the control voltage is obtained from an outside source to provide isolation between devices. A "wet" contact device provides the power to the device you want to control. Wet contact is like a mercury switch dry contact is like a relay.

R32 Refrigerant

GWP of 600 R32 refrigerant is also known as difluoromethane and belongs to the HFC family of refrigerant. This gas is poised to replace the other gaseous such as R-410A and R-407C as the preferred gas due to its lower Global Warming Potential. Its chemical formula is CH2F2.

8 oz of R-404a is equivalent to one ton of CO2.

GWP ratio between CO2 and 404a

zerk fitting

Grease fitting

load calc softwares

HAP and TRACE

does latent heat of vaporization change with pressure?

Increasing the pressure has the overall the effect of reducing the enthalpy of vaporization, until it becomes zero at the critical point. At this stage, there is no longer a phase change associated with vaporization. Let be simple. Latent heat refers to the heat required to overcome molecular bonds.

What is indirect refrigeration system? (indirect chiller)

Indirect expansion system. A refrigeration system in which a secondary coolant is cooled by the direct expansion of a primary refrigerant and is then circulated to cool the medium which absorbs heat from the space to be cooled.

inrush current

Initial surge of current when motor is started can be lowered by using a VFD usually 10 times higher than FLA

Dehumidification equation

Latent cooling / 1054 * 24 = # of pints for dehumidifier 1054 = how many BTU's it takes to remove a pint of water

Oil types

Mineral - a by-product in the distillation of crude oil to produce gasoline. Mineral oil can be classified into the following groups: naphthenic, paraffinic, and aromatic. Naphthene based mineral oils are suitable for refrigeration systems using CFC or HCFC refrigerants. Alkylbenzene (AB) - a synthetic oil suitable for refrigeration systems using CFC or HCFC refrigerants. It is compatible with mineral oil and compared to mineral oil, it has improved refrigerant miscibility with R-22 at low-temperature conditions. Polyolester (POE) - the primarily synthetic oil for refrigeration systems using HFC refrigerants. It is also suitable for refrigeration systems using CFC, HCFC refrigerants and being evaluated in CO2 systems. ​​Polyalkylene​ Glycol (PAG) - a synthetic oil primarily used in R-134a automotive air conditioning systems. It is more hygroscopic that either POE or PVE oils, but it does not undergo hydrolysis in the presence of water. Polyvinyl Ether (PVE) - a synthetic oil that is being used as an alternative to POE oil. It is more hygroscopic than POE oil but less than PAG oil. Like PAG oil, PVE oil does not undergo hydrolysis in the presence of water.

gearbox purpose

Most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft (e.g. a motor crankshaft). This means that the output shaft of a gearbox rotates at a slower rate than the input shaft, and this reduction in speed produces a mechanical advantage, increasing torque.

dangerous CO thresholds

Most people will not experience any symptoms from prolonged exposure to CO levels of approximately 1 to 70 ppm but some heart patients might experience an increase in chest pain. As CO levels increase and remain above 70 ppm, symptoms become more noticeable and can include headache, fatigue and nausea.

do nonpolar substances dissolve in water?

Nonpolar molecules do not dissolve easily in water. They are described as hydrophobic, or water fearing. When put into polar environments, such as water, nonpolar molecules stick together and form a tight membrane, preventing water from surrounding the molecule.

CO2 is a better secondary refrigerant than glycol. With glycol you can only remove heat sensibly. With CO2 it starts to boil so you absorb latent and sensible heat.

Not sure if this is correct. The numbers seem high. Cannot find the specific heat of either to verify. Look into.

District Geothermal

One large geothermal system is installed and then individual circuits are branched off from it to businesses or residences. This allows for a more convenient way to heat and cool homes while in tight living spaces.

standard pressure for pneumatic controls

Pneumatic system control air is usually 20 psig, so a pressure reducing station is needed. Through experience, certain criteria have been developed for the selection of a proper pneumatic system air compressor. An air compressor should be selected to run 1/3 to 1/2 of the time, based on average air consumption of a system. Average air consumption is expressed in standard cubic feet per minute - SCFM. Compressors are rated in SCFM at a given tank pressure, usually 80 psig. Sizing a compressor is matching the compressor capacity to a system's requirement. The consumption of each air-using device in a system is taken into consideration. Relays, thermostats, switches, transmitters, and all devices that use air must be considered, and the compressor should be sized so that when operating, 1/3 to 1/2 of the time it will deliver enough air to satisfy the average air requirement of a system. https://www.industrialcontrolsonline.com/training/online/learn-about-pneumatic-control-system-air-compressors

slab on grade

Slab-on-grade or floating slab foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. The concrete is then placed into the mold, leaving no space between the ground and the structure. A slab floor is a fantastic way to start a passive solar home, as your entire floor surface consists of several inches of thermal mass to absorb heat. ... A slab-on-grade means no basement, no basement walls, just one slab of concrete on which you build your house

storage heater

Storage heaters are typically composed of clay bricks or other ceramic material (grog), of concrete walls, or of water containers. There are also special materials such as feolite. This material serves as a heat storage medium. There are electrical heating elements embedded in the material which can be switched on to heat the storage medium and thus to store energy. The stored heat is given off continuously (through thermal radiation and convection). To speed up the heat transfer, storage heaters may come equipped with mechanical fans that can move air through the heater; see the section on fan-assisted storage heaters.

Supercooling

Supercooling,[1] also known as undercooling,[2] is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid. A liquid crossing its standard freezing point will crystalize in the presence of a seed crystal or nucleus around which a crystal structure can form creating a solid. Lacking any such nuclei, the liquid phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs. Homogeneous nucleation can occur above the glass transition temperature, but if homogeneous nucleation has not occurred above that temperature, an amorphous (non-crystalline) solid will form. Water normally freezes at 273.15 K (0 °C or 32 °F), but it can be "supercooled" at standard pressure down to its crystal homogeneous nucleation at almost 224.8 K (−48.3 °C/−55 °F).[3][4] The process of supercooling requires that water be pure and free of nucleation sites, which can be achieved by processes like reverse osmosis or chemical demineralization, but the cooling itself does not require any specialised technique. If water is cooled at a rate on the order of 106 K/s, the crystal nucleation can be avoided and water becomes a glass—that is, an amorphous (non-crystalline) solid. Its glass transition temperature is much colder and harder to determine, but studies estimate it at about 136 K (−137 °C/−215 °F).[5]Glassy water can be heated up to approximately 150 K (−123 °C/−189.4 °F) without nucleation occurring.[4] In the range of temperatures between 231 K (−42 °C/−43.6 °F) and 150 K (−123 °C/−189.4 °F), experiments find only crystal ice. Droplets of supercooled water often exist in stratus and cumulus clouds. An aircraft flying through such a cloud sees an abrupt crystallization of these droplets, which can result in the formation of ice on the aircraft's wings or blockage of its instruments and probes, unless the aircraft is equipped with an appropriate de-icing system. Freezing rain is also caused by supercooled droplets. The process opposite to supercooling, the melting of a solid above the freezing point, is much more difficult, and a solid will almost always melt at the same temperature for a given pressure. For this reason, it is the melting point which is usually identified, using melting point apparatus; even when the subject of a paper is "freezing-point determination", the actual methodology is "the principle of observing the disappearance rather than the formation of ice".[6] It is possible, at a given pressure, to superheat a liquid above its boiling point without it becoming gaseous. Supercooling is often confused with freezing-point depression. Supercooling is the cooling of a liquid below its freezing point without it becoming solid. Freezing point depression is when a solution can be cooled below the freezing point of the corresponding pure liquid due to the presence of the solute; an example of this is the freezing point depression that occurs when salt is added to pure water. In order to survive extreme low temperatures in certain environments, some animals use the phenomenon of supercooling that allow them to remain unfrozen and avoid cell damage and death. There are many techniques that aid in maintaining a liquid state, such as the production of antifreeze proteins, or AFPs, which bind to ice crystals to prevent water molecules from binding and spreading the growth of ice.[8] The winter flounder is one such fish that utilizes these proteins to survive in its frigid environment. Noncolligative proteins are secreted by the liver into the bloodstream.[9] Other animals use colligative antifreezes, which increases the concentration of solutes in their bodily fluids, thus lowering their freezing point. Fish that rely on supercooling for survival must also live well below the water surface, because if they came into contact with ice nuclei they would freeze immediately. Animals that undergo supercooling to survive must also remove ice-nucleating agents from their bodies because they act as a starting point for freezing. Supercooling is also common in insects, reptiles, and other ectotherms, with insects being able to survive in the coldest environments out of any supercooling animals. For instance, the potato cyst nematod larvas (Globodera rostochiensis) could survive inside their cysts in a supercooled state to temperatures as low as −38 °C (−36 °F), even with the cyst encased in ice. Supercooling is a last resort for animals. The best option is to move to a warmer environment if possible. As an animal gets farther and farther below its original freezing point the chance of spontaneous freezing increases dramatically for its internal fluids, as this is a thermodynamically unstable state. The fluids eventually reach the supercooling point, which is the temperature at which the supercooled solution freezes spontaneously due to being so far below its normal freezing point.[10] Animals unintentionally undergo supercooling and are only able to decrease the odds of freezing once supercooled. Even though supercooling is essential for survival, there are many risks associated with it. As demonstrated by animals, plants can also survive extreme cold conditions brought forth during the winter months. Many plant species located in northern climates can acclimate under these cold conditions by supercooling, thus these plants survive temperatures as low as −40 °C. Although this supercooling phenomenon is poorly understood, it has been recognized through infrared thermography. Ice nucleation occurs in certain plant organs and tissues, debatably beginning in the xylem tissue and spreading throughout the rest of the plant.[11][12] Infrared thermography allows for droplets of water to be visualized as they crystalize in extracellular spaces. Supercooling inhibits the formation of ice within the tissue by ice nucleation and allows the cells to maintain water in a liquid state and further allows the water within the cell to stay separate from extracellular ice.[13] Cellular barriers such as lignin, suberin and the cuticle inhibit ice nucleators and force water into the supercooled tissue.[14] The xylem and primary tissue of plants are very susceptible to cold temperatures because of the large proportion of water in the cell. Many boreal hardwood species in northern climates have the ability to prevent ice spreading into the shoots allowing the plant to tolerate the cold.[15] Supercooling has been identified in the evergreen shrubs Rhododendron ferrugineum and Vaccinium vitis-idaea as well as Abies, Picea and Larix species.[15] Freezing outside of the cell and within the cell wall does not affect the survival of the plant.[16] However, the extracellular ice may lead to plant dehydration. One commercial application of supercooling is in refrigeration. Freezers can cool drinks to a supercooled level[17] so that when they are opened, they form a slush. Another example is a product that can supercool the beverage in a conventional freezer.[18] The Coca-Cola Company briefly marketed special vending machines containing Sprite in the UK, and Coke in Singapore, which stored the bottles in a supercooled state so that their content would turn to slush upon opening.[19]

Superheated water

Superheated water is liquid water under pressure at temperatures between the usual boiling point, 100 °C (212 °F) and the critical temperature, 374 °C (705 °F). It is also known as "subcritical water" or "pressurized hot water." Superheated water is stable because of overpressure that raises the boiling point, or by heating it in a sealed vessel with a headspace, where the liquid water is in equilibrium with vapour at the saturated vapor pressure. This is distinct from the use of the term superheating to refer to water at atmospheric pressure above its normal boiling point, which has not boiled due to a lack of nucleation sites (sometimes experienced by heating liquids in a microwave). Many of water's anomalous properties are due to very strong hydrogen bonding. Over the superheated temperature range the hydrogen bonds break, changing the properties more than usually expected by increasing temperature alone. Water becomes less polar and behaves more like an organic solvent such as methanol or ethanol. Solubility of organic materials and gases increases by several orders of magnitude and the water itself can act as a solvent, reagent, and catalyst in industrial and analytical applications, including extraction, chemical reactions and cleaning.

end switch

Suppose you have a modulating motor with an arm that can rotate back and forth over a 90-degree range. Suppose you want to control dampers that will bind up if they are moved more than an 80-degree range. An 'End Switch' is an electric switch mounted on the motor linkage that will stop the motor movement when it reaches that 80-degree limit by opening the electrical circuit to the motor. Most companies that make the modulating motors supply these switches as an accessory. Actually, the linkages on the damper and motor are adjusted so that the damper movement is limited to something less that 90 deg, and that it does not stop on dead center.

AC Line Regenerative Module (line regen unit)

The Ac Line Regen Module turns any PWM AC Drive into a Line Regenerative Ac Drive. Excess (regenerative) energy from the AC Motor is efficiently returned to the AC Power Line, eliminating the need for expensive, bulky and inefficient braking resistors. This is especially true when continuous braking is required.

Ammonium

The ammonium cation is a positively charged polyatomic ion with the chemical formula NH⁺ ₄. It is formed by the protonation of ammonia.

what is chrome made of?

The chromium plating is usually applied over bright nickel plating. Typical base materials include steel, aluminium, plastic, copper alloys, and zinc alloys. Decorative chrome plating is also very corrosion resistant and is often used on car parts, tools and kitchen utensils. Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard and brittle transition metal. Chromium is the main additive in stainless steel, to which it adds anti-corrosive properties Chromium is found mainly in chromite. This ore is found in many places including South Africa, India, Kazakhstan and Turkey. Chromium metal is usually produced by reducing chromite with carbon in an electric-arc furnace, or reducing chromium(III) oxide with aluminium or silicon.

What You Need to Know About Flooded Head Pressure Control

The flooded head pressure control valve maintains head pressure by backing up liquid refrigerant into the condenser, and in doing so reduces condenser capacity. This function requires the system to have additional refrigerant available that it won't need during summertime operation when head pressure will be above the valve's control setting. This additional refrigerant must be stored in the receiver when it is not needed by the head pressure control valve.

compression ratio

Volume of combustion chamber at end of compression stroke as compared to volume of cylinder and chamber with piston on bottom center. Compression ratios usually range from 8:1 to 10:1. A higher compression ratio -- say, from 12:1 to 14:1 -- means higher combustion efficiency. Higher compression ratios and combustion efficiency mean more power with less fuel, and fewer exhaust gases. A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. This occurs because internal combustion engines are heat engines, and higher compression ratios permit the same combustion temperature to be reached with less fuel, while giving a longer expansion cycle, creating more mechanical power output and lowering the exhaust temperature. In a piston engine, the static compression ratio (CR) is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.[6] It is therefore calculated by the formula: Vd = displacement volume Vc = clearance volume

Armature

The rotating part of an electrical generator. The power-producing component of an electrical machine. In a generator, alternator, or dynamo, the armature windings generate the electric current, which provides power to an external circuit. The armature can be on either the rotor or the stator, depending on the design, with the field coil or magnet on the other part.

Magnetic moment

The strength of a magnetic field is known as the magnetic moment. Those with a weak attractive force are referred to as paramagnetic materials, while ferromagnetic materials have a strong attractive force. A diamagnetic material has electrons that are paired, and therefore does not typically have a magnetic moment. There are, however, some diamagnetic materials that have a weak magnetic field. The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include: loops of electric current, permanent magnets, moving elementary particles, various molecules, and many astronomical objects

Phase transition

The term phase transition (or phase change) is most commonly used to describe transitions between solid, liquid, and gaseous states of matter, as well as plasma in rare cases. A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium, certain properties of the medium change, often discontinuously, as a result of the change of external conditions, such as temperature, pressure, or others. For example, a liquid may become gas upon heating to the boiling point, resulting in an abrupt change in volume. The measurement of the external conditions at which the transformation occurs is termed the phase transition. Phase transitions commonly occur in nature and are used today in many technologies.

turbocharger used on generator

The turbocharger uses that energy—which is otherwise wasted—thereby increasing the efficiency of the engine and increasing power at the same time. ... Turbocharged engines are ideal for use in generators because they are efficient and borrow very little energy from the turning engine, unlike a supercharger.

Why do so many medications have "HCl" in them?

When they say "HCl" behind the name of a medication, they're referring to the hydrochloride salt. Many pharmaceutical agents have protonation sites, such as amines, and they can be prepared as a pure substance, or as an HCl salt - so instead of -NH₂, it will become -NH₃Cl. For particularly lipophilic drugs, this helps it dissolve in water, as the compound will dissociate into its constituent ammonium and chloride ions. One such example would be cocaine - in powder form, it is a hydrochloride salt. When you deprotonate the amine, you get the "free base" form, also known as crack cocaine.

Whole house humidifier

Whole-house humidifiers are common nowadays. They attach to your ductwork and blow moist air into your home, raising your relative humidity and, in theory, improving overall comfort.

NTC (negative temperature coefficient)

With NTC thermistors, resistance decreases as temperature rises. An NTC is commonly used as a temperature sensor, or in series with a circuit as an inrush current limiter. Many NTC thermistors are made from a pressed disc, rod, plate, bead or cast chip of semiconducting material such as sintered metal oxides. They work because raising the temperature of a semiconductor increases the number of active charge carriers[6] it promotes them into the conduction band. The more charge carriers that are available, the more current a material can conduct. In certain materials like ferric oxide (Fe2O3) with titanium (Ti) doping an n-type semiconductor is formed and the charge carriers are electrons. In materials such as nickel oxide (NiO) with lithium (Li) doping a p-type semiconductor is created, where holes are the charge carriers.[7]

PTC (positive temperature coefficient)

With PTC thermistors, resistance increases as temperature rises. PTC thermistors are commonly installed in series with a circuit, and used to protect against overcurrent conditions, as resettable fuses. Most PTC thermistors are made from doped polycrystalline ceramic (containing barium titanate (BaTiO3) and other compounds) which have the property that their resistance rises suddenly at a certain critical temperature. Barium titanate is ferroelectric and its dielectric constant varies with temperature. Below the Curie point temperature, the high dielectric constant prevents the formation of potential barriers between the crystal grains, leading to a low resistance. In this region the device has a small negative temperature coefficient. At the Curie point temperature, the dielectric constant drops sufficiently to allow the formation of potential barriers at the grain boundaries, and the resistance increases sharply with temperature. At even higher temperatures, the material reverts to NTC behaviour. Another type of thermistor is a silistor, a thermally sensitive silicon resistor. Silistors employ silicon as the semiconductive component material. Unlike ceramic PTC thermistors, silistors have an almost linear resistance-temperature characteristic. Barium titanate thermistors can be used as self-controlled heaters; for a given voltage, the ceramic will heat to a certain temperature, but the power used will depend on the heat loss from the ceramic.

baffle

restrain or regulate (a fluid, sound, etc.). "to baffle the noise further, I pad the gunwales"

CO2 specific gravity

same as propane (R-290): 1.51

recapping a system

swapping out the capacitors in a system that has been running for awhile "this system needs to be recapped"

hall effect

the creation of voltage across a current-carrying conductor by a magnetic field The Hall effect is the production of a voltage difference across an electrical conductor, transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current.

Vapor density

the density of a particular gas or vapor relative to that of hydrogen at the same pressure and temperature. Vapour density is the density of a vapour in relation to that of hydrogen. It may be defined as mass of a certain volume of a substance divided by mass of same volume of hydrogen. vapour density = mass of n molecules of gas / mass of n molecules of hydrogen vapour density = mass of n molecules of gas / mass of n molecules of hydrogen. Thus: vapour density = molar mass of gas / molar mass of H₂ vapour density = molar mass of gas / 2.016 For example, vapour density of mixture of NO2 and N2O4 is 38. 3. Vapour density is a unitless quantity. So ultimately what matters more is the specific volume. CO2 specific volume = 0.115 lbs / ft³ https://www.engineeringtoolbox.com/gas-density-d_158.html

triple point

the temperature and pressure conditions at which the solid, liquid, and gaseous phases of a substance coexist at equilibrium

spray foam home

tight house

charging chart

used to help charge a system.

Transite vs. sub-slab ducts

The two components in a home that are most appropriately called transite are cement-asbestos gas vents and cement-asbestos sub-slab ducts. That's right, most sub-slab ductwork here in Minnesota is not made from transite. It's mostly PVC. When this ductwork is called transite, it's implied that the ductwork contains asbestos. Don't call it transite if the ductwork is not made from cement-asbestos. This creates confusion and unnecessary concern. Call it sub-slab ductwork. Transite ductwork was used in the 1960's and early 1970's. So what's the concern with actual transite sub-slab ductwork? Asbestos. The cut edges of this material are often rough and have the potential to release microscopic asbestos particles into the air if disturbed. The term for this condition is "friable". This means that the ductwork probably shouldn't be cleaned, for risk of creating an environmental hazard. Don't expect your duct cleaner to know this, however. If you hire them to clean your ducts, they'll clean your ducts.

net zero homes

They are regular grid-tied homes that are so air-tight, well insulated, and energy efficient that they produce as much renewable energy as they consume over the course of a year, leaving the occupants with a net zero energy bill, and a carbon-free home. Many are skeptical of the claims that zero-energy homes can be built affordably. The details are below, but here's the bottom line, for today's average 2,400 new-construction home: Standard home: $240,000. Net zero energy home: $263,500

who made the refrigerator?

US physician John Gorrie built a refrigerator in 1844 based on the design of Oliver Evans to produce ice for cooling the air for yellow fever patients. The first ice making machine used for practical food purposes such as meat packing and brewing was invented by James Harrison in 1857.

jig saw

Used for cutting irregular shapes.

Electrostatic Filters

Uses static electricity to capture particulates as small as 10 microns Particles are attracted to charges opposite of their own

How can I figure out how much refrigerant I have in the receiver?

Using a torch (preferably a propane torch), GENTLY heat up the receiver while the system is running. Check the rated heat value for the receiver. Then run your hand from the bottom of the receiver to where you heated it. If the receiver is only warm, you have liquid present. If it is hot, you do not have liquid present. With a little practice, you should be able to accurately locate the refrigerant level using this technique.

VFD operation

VFD switching frequency refers to the rate at which the DC bus voltage is switched on and off during the pulse width modulation (PWM) process. The switching on and off of the DC voltage is done by Insulated Gate Bipolar Transistors (IGBTs). The PWM process utilizes the switching of the IGBT's to create the variable voltage and variable frequency output from the VFD for control of AC induction, permanent magnet synchronous or DC motors. The switching frequency, sometimes called the "carrier frequency", is defined using the unit of hertz (Hz) and is typically in the kHz (Hz*1000) range, typically ranging from 4 to 16khz, or 4000 to 16000 switches on/off per second. The harmonic content in the current waveform generated by the PWM process is reduced as the switching frequency increases. The 'cleaner' waveform results in higher efficiency by reducing the current ripple, which results in lower motor losses. This benefit of a higher switching frequency is more pronounced as the output frequency to the motor increases.

Variable compression ratio

Variable compression ratio is a technology to adjust the compression ratio of an internal combustion engine while the engine is in operation. This is done to increase fuel efficiency while under varying loads. Variable compression engines allow the volume above the piston at top dead centre to be changed. Higher loads require lower ratios to increase power, while lower loads need higher ratios to increase efficiency, i.e. to lower fuel consumption. For automotive use this needs to be done as the engine is running in response to the load and driving demands. The 2019 Infiniti QX50 is the first commercially available vehicle that uses a variable compression ratio engine.

panel link filter

Link Panel Filters. The M-3 Panels & Links are constructed with a premium grade, l00% polyester fiber, 3-stage media. ... Smaller particles are caught by the second ply of finer denier fibers. The final layer is a tightly needled matrix treated with a non-migrating tackifier to catch and hold the smallest particles. Polyester is a category of polymers that contain the ester functional group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. The material is used extensively in clothing. Polyester fibers are sometimes spun together with natural fibers to produce a cloth with blended properties. Cotton-polyester blends can be strong, wrinkle- and tear-resistant, and reduce shrinking. Synthetic fibers using polyester have high water, wind and environmental resistance compared to plant-derived fibers. They are less fire-resistant and can melt when ignited.[1]

Master control

A master controller is a controller which transmits its output signal to another controller (to the slave controller).

Motor encoders

A motor encoder is a rotary encoder mounted to an electric motor that provides closed loop feedback signals by tracking the speed and/or position of a motor shaft.

maximum amount of R-290 that can be used

EPA has a limit of 150 grams (5.29 ounces) on the amount of R-290 charge for self-contained commercial systems.

Single wave vs full wave rectifier

In half-wave rectification of a single-phase supply, either the positive or negative half of the AC wave is passed, while the other half is blocked. Mathematically, it is a step function (for positive pass, negative block): passing positive corresponds to the ramp function being the identity on positive inputs, blocking negative corresponds to being zero on negative inputs. Because only one half of the input waveform reaches the output, mean voltage is lower. Half-wave rectification requires a single diode in a single-phase supply, or three in a three-phase supply. Rectifiers yield a unidirectional but pulsating direct current; half-wave rectifiers produce far more ripple than full-wave rectifiers, and much more filtering is needed to eliminate harmonics of the AC frequency from the output. Can be done with single diode. A full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Mathematically, this corresponds to the absolute value function. Full-wave rectification converts both polarities of the input waveform to pulsating DC (direct current), and yields a higher average output voltage. Two diodes and a center tapped transformer, or four diodes in a bridge configuration and any AC source (including a transformer without center tap), are needed.[3] Single semiconductor diodes, double diodes with common cathode or common anode, and four-diode bridges, are manufactured as single components. Can be done with 4 diodes in a bridge rectifier

ductile

(of a metal) able to be drawn out into a thin wire. able to be deformed without losing toughness; pliable, not brittle.

How is static electricity used in spray painting?

- Spray gun charged. - Paint particles charged the same so they repel and give a fine spray. - Object charged oppositely to paint so attracts paint, giving an even coat and less waste.

Split system Air conditioning sequence of operation

- The thermostat, set to cooling mode, calls for cooling. The switch inside the thermostat closes. That energizes the "Y" and the "G" circuit in the thermostat or the compressor contactor and the fan circuit. - The compressor contactor closes, and the condenser fan motor and the compressor turns on. That happens simultaneously as the compressor contactor controls both the compressor and the condenser fan motor. That is important because if the compressor contactor pulls in or engages and the fan doesn't start, but the compressor does, then the technician knows there is a problem with the condenser fan motor and vice versa. If neither starts, but the contactor is pulled in, then the technician knows there is either a problem with the contactor passing voltage across the contacts or a power problem. If the contactor does not pull-in, then the tech knows there is a control problem.Condenser - Air Conditioner - Heat Pump Fan Motor - At the same time the compressor contactor is doing its job, the blower fan relay closes (from the "G" contact in the thermostat) and energizes the blower fan. While the compressor gets the refrigerant moving through the refrigeration system, the fan begins moving air through the duct system and across the evaporator coil. - When the thermostat satisfies the "Y" and the "G" contacts in the thermostat open de-energizing the compressor contactor and the fan relay. The compressor and condenser fan motor de-energize and stop operation. The fan, in heating and cooling mode (no matter what type of heat you have), will remain on because of a time delay in the air handler. That is to dissipate any cool or hot air left in the duct system. It adds efficiency to the system and makes use of any residual energy left in the system. In heating mode, it also allows for a cooling down of the heat left in the system.

Ductile Iron

-add Mg and/or Ce -graphite as nodules not flakes -matrix often pearlite - stronger but less ductile Ductile Iron is a type of cast iron known for its impact and fatigue resistance, elongation, and wear resistance due to the spherical (round) graphite structures in the metal. Ductile Iron is also called ductile cast iron, spheroidal graphite cast iron, or nodular cast iron. While most varieties of cast iron are weak in tension and brittle, ductile iron has much more impact and fatigue resistance, due to its nodular graphite inclusions. The common defining characteristic of this group of materials is the shape of the graphite. In ductile irons, graphite is in the form of nodules rather than flakes as in grey iron. Whereas sharp graphite flakes create stress concentration points within the metal matrix, rounded nodules inhibit the creation of cracks, thus providing the enhanced ductility that gives the alloy its name.

"if somethings difficult, you're probably doing it wrong"

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A motor with more poles has a higher torque and a lower speed. When you have a motor with more poles it replaces the need for a gearbox.

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car battery voltage

12 volts DC

A number of technologies have been developed to help increase the efficiency of transcritical CO2 refrigeration systems, especially in high ambient conditions. When the ambient temperature is higher than the critical point of CO2 (88°F/31°C), CO2 enters the supercritical phase and can't be fully condensed. It can be cooled, and the cooled gas-liquid mixture is further treated to create liquid CO2 for the evaporator. Adiabatic gas coolers, ejectors, parallel compression and subcooling are some of the key technologies that are used to reduce the workload in a transcritical CO2 system in high ambients, thereby improving its efficiency. A new research paper proposes another method: the use of an absorption chiller for subcooling. The paper, "Enhancing the performance of a CO2 refrigeration system with the use of an absorption chiller," was published in the December issue of the International Journal of Refrigeration and can be accessed here. In this scenario, an absorption chiller, which does not use a compressor, is fed by waste heat generated by the transcritical compressors. The authors of the study - Evangelos Bellos and Christos Tzivanidis of the Thermal Department, School of Mechanical Engineering, National Technical University of Athens - found that in all cases, the examined system is more efficient than the reference, with a mean COP (coefficient of performance) enhancement of about 23% and a maximum improvement of 75%. The enhancements are greater in the cases with a higher compressor pressure ratio.

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Anyone here have aspergers? No? Good. Because we need full spectrum here, not half.

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CO2 does not operate anywhere close to the pressures needed to chop your fingers off. Pat is a frickin moron. Supposedly you would need an excess of 7000 psi to chop through finger bone. However, CO2 pressures would be high enough to pierce skin.

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Complexity impresses your peers. Clarity impresses your customers.

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Ductless mini-split systems work off time based dehumidification. Make sure to add on a humidification sensor so the system is not running randomly. Also the condensate lines are tiny, the diameter of a pencil, on these systems so maybe increase the size if possible?

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For Vacuums: Heating up the compressor can help release non-condensables that are trapped in oil. Nitrogen gets trapped in oil during pressure tests.

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I would rather ask a seemingly stupid question than not ask it and make a stupid mistake.

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In order to remove humidity, equipment needs to run longer. Short cycling does not remove humidity.

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Listening to a podcast a while back, they shared an acronym for the sequence of an Integrated Furnace Control and it went like this "Take It Slow Its Gonna Blow" , "T" is Thermostat , "I" is Inducer Motor , "S" is Safety (Pressure Switch) , "I" is Ignition , "G" is Gas , and finally "B" is Blower Motor" Hope it helps !

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Make sure to pat down a condenser after washing the coil and before starting the unit. If you don't, the head pressure will be high. If you mist a condenser coil with water you can lower the condenser head pressure by evaporating the water off of the condenser coil.

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Thumb-rule 400 cfm per ton of cooling is needed for normal comfort applications, 500 cfm per ton of cooling for heat pump and high sensible heat applications, and 350 cfm per ton of cooling for high latent heat applications

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UV water purification can be used on boats. This would allow you to drink water straight from the lake. A UV water purifier treats microbiologically unsafe water with germicidal ultraviolet light. The UV wavelength scrambles the DNA of living organisms in the water, so they can no longer reproduce and make you sick. If you drink bacteria-infested water, the organisms can embed in your digestive tract and replicate.

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How many pints equal a pound?

1 pint = 1 pound

What percent of the time does equipment run at peak load?

1% of the time. 99% of the time the equipment is oversized.

What temperature does copper melt at?

1,984°F

5-HT receptor

5-hydroxytryptamine receptors or 5-HT receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels found in the central and peripheral nervous systems.[1][2][3] They mediate both excitatory and inhibitory neurotransmission. The serotonin receptors are activated by the neurotransmitter serotonin, which acts as their natural ligand. The serotonin receptors modulate the release of many neurotransmitters, including glutamate, GABA, dopamine, epinephrine / norepinephrine, and acetylcholine, as well as many hormones, including oxytocin, prolactin, vasopressin, cortisol, corticotropin, and substance P, among others. The serotonin receptors influence various biological and neurological processes such as aggression, anxiety, appetite, cognition, learning, memory, mood, nausea, sleep, and thermoregulation. The serotonin receptors are the target of a variety of pharmaceutical and recreational drugs, including many antidepressants, antipsychotics, anorectics, antiemetics, gastroprokinetic agents, antimigraine agents, hallucinogens, and entactogens. Serotonin receptors are found in almost all animals and are even known to regulate longevity and behavioral aging in the primitive nematode, Caenorhabditis elegans.[5][6]

What is the triple point of CO2?

61 psig The Triple Point for carbon dioxide is 5.1 atm at a temperature of -56.6C (-69.8°F). At one atmosphere pressure, carbon dioxide freezes, or sublimes, at -78.5C (-109.2°F).

supercritical water temp

705 °F 3212 psig

Brushless DC electric motor

A brushless DC electric motor (BLDC motor or BL motor), also known as electronically commutated motor (ECM or EC motor) and synchronous DC motors, are synchronous motors powered by direct current (DC) electricity via an inverter or switching power supply which produces an alternating current (AC) electric current to drive each phase of the motor via a closed loop controller. The controller provides pulses of current to the motor windings that control the speed and torque of the motor. The construction of a brushless motor system is typically similar to a permanent magnet synchronous motor (PMSM), but can also be a switched reluctance motor, or an induction (asynchronous) motor. The advantages of a brushless motor over brushed motors are high power-to-weight ratio, high speed, electronic control, and low maintenance. Brushless motors find applications in such places as computer peripherals (disk drives, printers), hand-held power tools, and vehicles ranging from model aircraft to automobiles. Beneficial that it doesn't have brushes since the soft brush material wears down due to friction, creating dust, and eventually the brushes must be replaced. This makes commutated motors unsuitable for low particulate or sealed applications like hard disk motors, and for applications that require maintenance free operation.

Esterification

A chemical reaction between an alcohol and an acid, in which an ester is formed. Esterification - the reverse of hydrolysis. It is the process in which an organic acid and alcohol are combined to form POE oil and water.

Compensation winding

A compensation winding in a DC shunt motor is a winding in the field pole face plate that carries armature current to reduce stator field distortion. Its purpose is to reduce brush arcing and erosion in DC motors that are operated with weak fields, variable heavy loads or reversing operation such as steel-mill motors. When flux from the armature current is about equal to the flux from the field current, the flux at the field pole plate is shifted. Under a fixed load, there is an optimal commutation point for the brushes that minimizes arcing and erosion of the brushes. When the ratio of armature flux to field flux varies greatly or reverses, the optimum commutation point shifts as result of the varying flux at the pole face plate. The result is arcing of the brushes. By adding a compensating winding in the pole face plate that carries armature current in the opposite direction of current in the adjacent armature windings, the position of the flux at the pole face plate can be restored to the position it would have with zero armature current. The main drawback of a compensation winding is the expense.

Passive infrared sensor

A passive infrared sensor is an electronic sensor that measures infrared light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors are commonly used in security alarms and automatic lighting applications.

Carbon tracking

A condition that occurs when spark jumps from a distributor cap terminal to another terminal or to ground. They appear as thin black lines on the inside of the cap. So what is carbon tracking? When a contactor is de-energized and pulls away, there is an arc that is created, a bi-product from the hot electrical arc is carbon. Carbon collects and builds on the contactor over time. If enough carbon is allowed to build it can create a path across power legs or to the panel that the contactor is mounted to, which is grounded. This path is considered to be a short, what happens when power is shorted to ground or across power legs? Boom goes the dynamite...That's what happens. Something to keep in mind though, I have never encountered blown fuses from carbon tracking from a unit installed indoors. Why, it doesn't rain inside. What I mean by that is, outdoor units are exposed to the elements. On a damp day, when moisture content is high in the air, that moisture embeds itself within the carbon track creating a conductive path. Dust can also contribute to this issue, for instance, if a unit electrical panel is under a negative due to the blower fan, dust can be pulled into the cabinet and create the same result.

water hammer arrestor

A device utilized to absorb the pressure surge (water hammer) that occurs when water flow is suddenly stopped in a water supply system.

Diode

A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p-n junction connected to two electrical terminals.[5] Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other materials such as gallium arsenide and germanium are also used.[6]

flange bearing

A flanged, open bearing. Flanged bearings are most commonly used in light duty applications, such as food processing machinery, conveyors, material handling, belt drives in HVAC, textile, baggage systems, medical processing and various other light duty industrial applications. flange: a projecting flat rim, collar, or rib on an object, serving to strengthen or attach or (on a wheel) to maintain position on a rail.

ground fault

A ground fault is an inadvertent contact between an energized conductor and ground or equipment frame. The return path of the fault current is through the grounding system and any personnel or equipment that becomes part of that system. Ground faults are frequently the result of insulation breakdown.

Heat pump

A heat pump is a device that transfers heat energy from a source of heat to what is called a thermal reservoir. Heat pumps move thermal energy in the opposite direction of spontaneous heat transfer, by absorbing heat from a cold space and releasing it to a warmer one. A heat pump uses external power to accomplish the work of transferring energy from the heat source to the heat sink.[1] The most common design of a heat pump involves four main components - a condenser, an expansion valve, an evaporator and a compressor. The heat transfer medium circulated through these components is called refrigerant. a cold space and releasing it to a warmer one. This process requires some amount of external energy, such as electricity. In heating, ventilation and air conditioning (HVAC) systems, the term heat pump usually refers to vapor-compression refrigeration devices optimized for high efficiency in both directions of thermal energy transfer. That is, heat pumps able to provide heating or cooling to the internal space as required. Heat pumps are more efficient for heating than resistance heaters because most of the energy they release comes from the ambient environment, and only a fraction from the externally-supplied energy required to run the device. In electrically-powered heat pumps, the heat transferred can be three or four times larger than the electrical power consumed, giving the system a coefficient of performance (COP) of 3 or 4, as opposed to a COP of 1 for a conventional electrical resistance heater, in which all heat is produced from input electrical energy. Heat pumps work like refrigerators, inside-out. They use a refrigerant as an intermediate fluid to absorb heat where it vaporizes, in the evaporator, and then to release heat where the refrigerant condenses, in the condenser. The refrigerant flows through insulated pipes between the evaporator and the condenser, allowing for efficient thermal energy transfer at relatively long distances. The simpler heat pumps tap the atmosphere as heat source; for better performance and greater energy flow, ground water or geothermal energy will be tapped, but this requires more expensive installation. The heat can be released directly into the air (this is simpler and cheaper), or through the water plumbing of central heating or to provide domestic hot water. Heat pumps take advantage of low temperature underfloor heating, because COP can be higher when the temperature difference is lower. Reversible heat pumps Reversible heat pumps work in either direction to provide heating or cooling to the internal space. They employ a reversing valve to reverse the flow of refrigerant from the compressor through the condenser and evaporation coils. In heating mode, the outdoor coil is an evaporator, while the indoor is a condenser. The refrigerant flowing from the evaporator (outdoor coil) carries the thermal energy from outside air (or soil, or better still, moving water) indoors. Vapor temperature is augmented within the pump by compressing it. The indoor coil then transfers thermal energy (including energy from the compression) to the indoor air, which is then moved around the inside of the building by an air handler. Alternatively, thermal energy is transferred to water, which is then used to heat the building via radiators or underfloor heating. The heated water may also be used for domestic hot water consumption. The refrigerant is then allowed to expand, and hence cool, and absorb heat from the outdoor temperature in the outside evaporator, and the cycle repeats. This is a standard refrigeration cycle, save that the "cold" side of the refrigerator (the evaporator coil) is positioned so it is outdoors where the environment is colder. In cold weather, the outdoor unit of an air source heat pump needs to be intermittently defrosted. This will cause the auxiliary or emergency heating elements (located in the air-handler) to be activated. At the same time, the frost on the outdoor coil will quickly be melted due to the warm refrigerant. The condenser/evaporator (outdoor) fan will not run during defrost mode. The indoor fan continues to run during the defrost cycle. In cooling mode the cycle is similar, but the outdoor coil is now the condenser and the indoor coil (which reaches a lower temperature) is the evaporator. This is the familiar mode in which air conditioners operate.

why do diodes emit light?

A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. Essentially the electrons break free from one side of the diode and then have to quickly put on the brakes to slide into the holes on the other side. They put on the brakes by emitting photons.

Photoresistor

A photoresistor (or light-dependent resistor, LDR, or photo-conductive cell) is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity. A photoresistor can be applied in light-sensitive detector circuits, and light-activated and dark-activated switching circuits. The light generates electron-hole pairs. Usually, electrons are more mobile and maintain the current while holes are much less mobile or simply stay trapped. There are three important constants to keep in mind : t1 = dielectric relaxation time and t2 non-equilibrium carrier lifetime, t3 = average transit time of carriers For most photoresistors t1<<t2 (neutralization by injection of electrons to compensate for the fixed holes happens fast enough). Such condition allows to obtain overall integrated signal current (signal charge) much higher than corresponding charge of initially generated carriers. That is because the current going to persist for ~ t2 time. This phenomena called 'photoconductance gain' , it may reach many thousand. Usually it can be estimated as t2/t3. Thanks for that, before transistors, photoresistors were used to directly drive electromechanical relays. Generally, both t1 and t2 might be strongly modulated by illumination leading to more complicated cases (e.g. quadratic recombination). Also, under strong enough external voltage the photo resistor may experience 'carrier sweep-out' CAD cell is a photoresistor

pillow block bearing

A piece that is used to hold a moving piece (such as an axle) in place relative to the rest of the system.

Polytropic process

A polytropic process is a thermodynamic process that obeys the relation: where p is the pressure, V is volume, n is the polytropic index, and C is a constant. The polytropic process equation can describe multiple expansion and compression processes which include heat transfer. The term "polytropic" was originally coined to describe any reversible process on any open or closed system of gas or vapor which involves both heat and work transfer, such that a specified combination of properties were maintained constant throughout the process.

Pressure-volume diagram (PV diagram)

A pressure-volume diagram (or PV diagram, or volume-pressure loop) is used to describe corresponding changes in volume and pressure in a system. They are commonly used in thermodynamics, cardiovascular physiology, and respiratory physiology.

Adiabatic process

A process in which no heat is transferred to or from the system by its surroundings. An adiabatic process occurs without transfer of heat or mass of substances between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred to the surroundings only as work. The adiabatic process provides a conceptual basis for the theory used to expound the first law of thermodynamics, and as such it is a key concept in thermodynamics.

Isobaric process

A process that occurs at a constant pressure

Quartz clock

A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than mechanical clocks. Generally, some form of digital logic counts the cycles of this signal and provides a numeric time display, usually in units of hours, minutes, and seconds. Chemically, quartz is a specific form of a compound called silicon dioxide. Many materials can be formed into plates that will resonate. However, quartz is also a piezoelectric material: that is, when a quartz crystal is subject to mechanical stress, such as bending, it accumulates electrical charge across some planes. In a reverse effect, if charges are placed across the crystal plane, quartz crystals will bend. Since quartz can be directly driven (to flex) by an electric signal, no additional transducer is required to use it in a resonator. Similar crystals are used in low-end phonograph cartridges: The movement of the stylus (needle) flexes a quartz crystal, which produces a small voltage, which is amplified and played through speakers. Quartz microphones are still available, though not common. Quartz has a further advantage in that its size does not change much as temperature fluctuates. Fused quartz is often used for laboratory equipment that must not change shape along with the temperature. A quartz plate's resonance frequency, based on its size, will not significantly rise or fall. Similarly, since its resonator does not change shape, a quartz clock will remain relatively accurate as the temperature changes. The electronic circuit is an oscillator, an amplifier whose output passes through the quartz resonator. The resonator acts as an electronic filter, eliminating all but the single frequency of interest. The output of the resonator feeds back to the input of the amplifier, and the resonator assures that the oscillator "howls" with the exact frequency of interest. When the circuit starts up, even a single shot can cascade to bringing the oscillator to the desired frequency. If the amplifier is too perfect, the oscillator will not start. The frequency at which the crystal oscillates depends on its shape, size, and the crystal plane on which the quartz is cut. The positions at which electrodes are placed can slightly change the tuning as well. If the crystal is accurately shaped and positioned, it will oscillate at a desired frequency. In nearly all quartz watches, the frequency is 32768 Hz,[3] and the crystal is cut in a small tuning fork shape on a particular crystal plane. This frequency is a power of two (32768 = 215), just high enough to exceed the human hearing range, yet low enough to permit inexpensive counters to derive a 1-second pulse.[4] A 15-bit binary digital counter driven by the frequency will overflow once per second, creating a digital pulse once per second. The pulse-per-second output can be used to drive many kinds of clocks. Although quartz has a very low coefficient of thermal expansion, temperature changes are the major cause of frequency variation in crystal oscillators. The most obvious way of reducing the effect of temperature on oscillation rate is to keep the crystal at a constant temperature. For laboratory-grade oscillators an oven-controlled crystal oscillator is used, in which the crystal is kept in a very small oven that is held at a constant temperature. This method is, however, impractical for consumer quartz clock and wrist-watch movements.

Repulsion motor

A repulsion motor is a type of electric motor which runs on alternating current (AC). It was formerly used as a traction motor for electric trains (e.g. SR Class CP and SR Class SL electric multiple units) but has been superseded by other types of motors. Repulsion motors are classified under single phase motors. In repulsion motors the stator windings are connected directly to the AC power supply and the rotor is connected to a commutator and brush assembly, similar to that of a direct current (DC) motor. The motor has a stator and a rotor but there is no electrical connection between the two and the rotor current is generated by induction. The rotor winding is connected to a commutator which is in contact with a pair of short-circuited brushes which can be moved to change their angular position relative to an imaginary line drawn through the axis of the stator. The motor can be started, stopped and reversed, and the speed can be varied, simply by changing the angular position of the brushes. Most commutator motors are limited to about 1,500 volts because higher voltages give rise to a risk of arcing across the commutator. Repulsion motors can be used at higher voltages because the rotor circuit is not electrically connected to the supply.

pulley vs shiv

A sheave () is a pulley with a grooved wheel for holding a belt, wire rope, or rope. The grooved wheel spins on an axle or bearing inside the frame of the block. ... Sheaves can be used to redirect a cable or rope, lift loads, and transmit power. The words sheave and pulley are sometimes used interchangeably.

Squirrel-cage rotor

A squirrel-cage rotor is the rotating part of the common squirrel-cage induction motor. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. In operation, the non-rotating stator winding is connected to an alternating current power source; the alternating current in the stator produces a rotating magnetic field. The rotor winding has current induced in it by the stator field, like a transformer except that the current in the rotor is varying at the stator field rotation rate minus the physical rotation rate. The interaction of the magnetic fields of currents in the stator and rotor produce a torque on the rotor. By adjusting the shape of the bars in the rotor, the speed-torque characteristics of the motor can be changed, to minimize starting current or to maximize low-speed torque, for example.

why use hot water boiler over steam?

A steam boiler must burn more fuel (gas or oil) to raise the temperature of its water to boiling level, and this makes hot water boilers more energy efficient, using approximately 25% less energy than steam boilers. For many homes, this is significant enough to prefer hot water over steam.

Supercritical fluid

A supercritical fluid (SCF[1]) is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. It can effuse through solids like a gas, and dissolve materials like a liquid. In addition, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be "fine-tuned". Supercritical fluids occur in the atmospheres of the gas giants Jupiter and Saturn, and probably in those of the ice giants Uranus and Neptune. In a range of industrial and laboratory processes, they are used as a substitute for organic solvents. Carbon dioxide and water are the most commonly used supercritical fluids, being used for decaffeination and power generation, respectively. The advantages of supercritical fluid extraction (compared with liquid extraction) are that it is relatively rapid because of the low viscosities and high diffusivities associated with supercritical fluids. The extraction can be selective to some extent by controlling the density of the medium, and the extracted material is easily recovered by simply depressurizing, allowing the supercritical fluid to return to gas phase and evaporate leaving little or no solvent residues. Carbon dioxide is the most common supercritical solvent. It is used on a large scale for the decaffeination of green coffee beans, the extraction of hops for beer production,[8] and the production of essential oils and pharmaceutical products from plants.[9] A few laboratory test methods include the use of supercritical fluid extraction as an extraction method instead of using traditional solvents. Supercritical water can be used to decompose biomass via supercritical water gasification of biomass.[13] This type of biomass gasification can be used to produce hydrocarbon fuels for use in an efficient combustion device or to produce hydrogen for use in a fuel cell. In the latter case, hydrogen yield can be much higher than the hydrogen content of the biomass due to steam reforming where water is a hydrogen-providing participant in the overall reaction. Supercritical carbon dioxide (SCD) can be used instead of PERC (perchloroethylene) or other undesirable solvents for dry-cleaning. Supercritical carbon dioxide sometimes intercalates into buttons, and, when the SCD is depressurized, the buttons pop, or break apart. Detergents that are soluble in carbon dioxide improve the solvating power of the solvent. Supercritical fluid chromatography (SFC) can be used on an analytical scale, where it combines many of the advantages of high performance liquid chromatography (HPLC) and gas chromatography (GC). It can be used with non-volatile and thermally labile analytes (unlike GC) and can be used with the universal flame ionization detector (unlike HPLC), as well as producing narrower peaks due to rapid diffusion. In practice, the advantages offered by SFC have not been sufficient to displace the widely used HPLC and GC, except in a few cases such as chiral separations and analysis of high-molecular-weight hydrocarbons.[15] For manufacturing, efficient preparative simulated moving bed units are available.[16] The purity of the final products is very high, but the cost makes it suitable only for very high-value materials such as pharmaceuticals.

Thermodynamic cycle

A thermodynamic cycle consists of a linked sequence of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state.[1] In the process of passing through a cycle, the working fluid (system) may convert heat from a warm source into useful work, and dispose of the remaining heat to a cold sink, thereby acting as a heat engine. Conversely, the cycle may be reversed and use work to move heat from a cold source and transfer it to a warm sink thereby acting as a heat pump. At every point in the cycle, the system is in thermodynamic equilibrium, so the cycle is reversible (its entropy change is zero, as entropy is a state function).

Why does my propane tank get frosty after using it?

All the answers about gas laws are very common, though, incorrect. Your tank of propane isn't just a tank full of gas - the propane is compressed under such high pressure that it is in liquid phase. You can hear it sloshing around when you move the tank. When a liquid evaporates, it cool down the liquid - this is called evaporative cooling. It's the same phenomenon that makes an ethanol swab feel cool on your skin. When you use the propane tank, you're draining the propane gas from the headspace of the tank - this decreases the pressure of the tank. Because propane is only liquid under pressure, this decrease will lead to some of that liquid evaporating. This is what cools down the tank. If you notice closely, you may even see the level of liquid propane inside the tank as the frost outside will only form below that liquid line. The other answers mention gas laws. While these laws are real, they're not largely responsible for the temperature change, because the heat change due to that is very small compared to that of the enthalpy of vaporization. Enthalpy change due to phase transition - like evaporative cooling - on the other hand, is less commonly encountered.

ammonia piping

Ammonia is a very caustic chemical and ammonia systems must be made with steel or nickel. No copper or copper-based piping can be used.

active sensor

An active sensor is a sensing device that requires an external source of power to operate; active sensors contrast with passive sensors, which simply detect and respond to some type of input from the physical environment. active sensor-based technologies include: scanning electron microscopes, LiDAR, radar, GPS, x-ray, sonar, infrared and seismic. ... Depending on what is being sensed, these various sensors might be mounted to a satellite, an airplane, a boat or a submarine UAV drone.

Alternator

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current.[2] For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.[3] Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines. An alternator that uses a permanent magnet for its magnetic field is called a magneto. Alternators in power stations driven by steam turbines are called turbo-alternators. Large 50 or 60 Hz three-phase alternators in power plants generate most of the world's electric power, which is distributed by electric power grids.

Autoclave

An autoclave is a pressure chamber used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient. Autoclaves are used in medical applications to perform sterilization and in the chemical industry to cure coatings and vulcanize rubber and for hydrothermal synthesis. Industrial autoclaves are used in industrial applications, especially in the manufacturing of composites. Many autoclaves are used to sterilize equipment and supplies by subjecting them to pressurized saturated steam at 121 °C (250 °F) for around 15-20 minutes depending on the size of the load and the contents [1] The autoclave was invented by Charles Chamberland in 1884,[2] although a precursor known as the steam digester was created by Denis Papin in 1679.[3] The name comes from Greek auto-, ultimately meaning self, and Latin clavis meaning key, thus a self-locking device. Sterilization autoclaves are widely used in microbiology, medicine, podiatry, tattooing, body piercing, veterinary medicine, mycology, funerary practice, dentistry, and prosthetics fabrication. They vary in size and function depending on the media to be sterilized and are sometimes called retort in the chemical and food industries.

Electric motor

An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of rotation of a shaft. Electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as a power grid, inverters or electrical generators. An electric generator is mechanically identical to an electric motor, but operates in the reverse direction, converting mechanical energy into electrical energy.

throttling valve

An isenthalpic process occurs in which of the following devices? A throttling valve is any device that reduces, increases, starts, or stops flow of a fluid. (in the case of a carburetor, air is considered a fluid, go figure). So, the plate in the base of a carburetor that opens and closes is a throttling valve.

Chlorine trifluoride

Chlorine trifluoride is so flammable it can burn through a foot of concrete and set sand on fire beneath it before burning out! It's so dangerous even the Nazis thought it's best to leave it alone Chlorine trifluoride is an interhalogen compound with the formula ClF₃. This colorless, poisonous, corrosive, and extremely reactive gas condenses to a pale-greenish yellow liquid, the form in which it is most often sold. It is fantastically reactive actually causing oxides to ignite. Glass, silicon dioxide, bursts into flame when in contact with it. Tissue, that is flesh, bursts into flame in contact with it. If it caused a fire, water or CO2 either of which are used to put out fires, both will catch fire on contact with this stuff. In addition to burning most everything it touches, it is also terribly toxic. As an inhalation hazard, it can destroy your lungs with a single breath! At lower concentration you might breath it and then later develop chemical pneumonia which is incurable. If supportive treatment works you live, otherwise...you don't. In your lungs, the ClF3 reacts with the water in your lungs forming HCl and HF-better known as hydrochloric acid and hydrofluoric acid. Imagine how well the very delicate cells in your lungs appreciate being in contact with two very powerful mineral acids. (Hint:they don't like it. They die.) Contact with your skin instantly causes thermal and chemical burns. Thermal because the CF3 reacts with the water literally causing the water to burn, and then chemical because HCl (hydrochloric acid) is being generated on the skin by the combustion of the water. This is a super oxidizer and somewhat like oxygen on steroids, except that whatever the oxygen burned, will burn AGAIN in chlorine trifluoride! By now you should be getting the idea that this is the perfect stuff to stay away from. Far, far away from. Use it to blind the Eye of Sauron.

amperage relation to air temp

Higher amperage for cool air of the same volume as warm air. Since air expands as it heats up, there is less of a load on the system when moving warm air.

Deposition (phase transition)

Deposition is the phase transition in which gas transforms into solid without passing through the liquid phase. Deposition is a thermodynamic process. The reverse of deposition is sublimation and hence sometimes deposition is called desublimation. One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid. This is how frost and hoar frost form on the ground or other surfaces. Another example is when frost forms on a leaf. For deposition to occur, thermal energy must be removed from a gas. When the air becomes cold enough, water vapor in the air surrounding the leaf loses enough thermal energy to change into a solid. Even though the air temperature may be below the dew point, the water vapor may not be able to condense spontaneously if there is no way to remove the latent heat. When the leaf is introduced, the supercooled water vapor immediately begins to condense, but by this point is already past the freezing point. This causes the water vapor to change directly into a solid. Another example is the soot that is deposited on the walls of chimneys. Soot molecules rise from the fire in a hot and gaseous state. When they come into contact with the walls they cool, and change to the solid state, without formation of the liquid state. The process is made use of industrially in combustion chemical vapor deposition. There is an industrial coatings process, known as evaporative deposition, whereby a solid material is heated to the gaseous state in a low-pressure chamber, the gas molecules travel across the chamber space and then condense to the solid state on a target surface, forming a smooth and thin layer on the target surface. Again, the molecules do not go through an intermediate liquid state when going from the gas to the solid. See also physical vapor deposition, which is a class of processes used to deposit thin films of various materials onto various surfaces. Deposition releases energy and is an exothermic phase change.

Oil properties

Dielectric Strength - a measure of the oil's resistance to an electric current. A low dielectric strength is indicative of moisture and/or contamination in the oil. Fire Point - the lowest temperature at which the oil maintains combustion. Flash Point - the lowest temperature at which oil vapor momentarily ignites. Floc Point - the temperature at which wax will separate from the oil. Above this temperature, the wax will remain in solution. Pour Point - the temperature at which the oil begins to pour. Specific Gravity - density with respect to water. Viscosity - a measure of the oil's resistance to flow. Two units of measure are typically used with refrigeration oil. The older measure is Saybolt Universal Seconds (SUS); the newer is ISO viscosity grade number (ISO VG), a measure using centistokes. For comparison, an oil having a 150 SUS has an ISO viscosity grade of 32.

direct acting vs pilot operated solenoids

Direct acting - Energizing the coil directly opens the main port of the valve allowing full flow. A direct acting valve pulls the plunger against inlet pressure and is typically limited to small applications or where there is a low-pressure differential across the valve. Pilot operated - Energizing the coil opens a pilot port which releases pressure above the main disc/piston/diaphragm allowing it to move to an open position for full flow. A pilot operated valve makes use of pressure differential across the valve to allow for higher flow capacities without the need of a large solenoid coil.

What is discus compressor?

Discus compressors are refrigeration compressors used in supermarkets, walk-in coolers and freezers, and industrial applications. They range in horsepower from 5 to 60-hp. Discus compressors are available with capacity modulation from 10 to 100 percent.

Doubly-fed electric machine

Doubly-fed electric machines also slip-ring generators are electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine. By feeding adjustable frequency AC power to the field windings, the magnetic field can be made to rotate, allowing variation in motor or generator speed. This is useful, for instance, for generators used in wind turbines. Doubly fed electrical generators are similar to AC electrical generators, but have additional features which allow them to run at speeds slightly above or below their natural synchronous speed. This is useful for large variable speed wind turbines, because wind speed can change suddenly. When a gust of wind hits a wind turbine, the blades try to speed up, but a synchronous generator is locked to the speed of the power grid and cannot speed up. So large forces are developed in the hub, gearbox, and generator as the power grid pushes back. This causes wear and damage to the mechanism. If the turbine is allowed to speed up immediately when hit by a wind gust, the stresses are lower with the power from the wind gust still being converted to useful electricity. One approach to allowing wind turbine speed to vary is to accept whatever frequency the generator produces, convert it to DC, and then convert it to AC at the desired output frequency using an inverter. This is common for small house and farm wind turbines. But the inverters required for megawatt-scale wind turbines are large and expensive. Doubly fed generators are another solution to this problem. Instead of the usual field winding fed with DC, and an armature winding where the generated electricity comes out, there are two three-phase windings, one stationary and one rotating, both separately connected to equipment outside the generator. Thus the term doubly fed. One winding is directly connected to the output, and produces 3-phase AC power at the desired grid frequency. The other winding (traditionally called the field, but here both windings can be outputs) is connected to 3-phase AC power at variable frequency. This input power is adjusted in frequency and phase to compensate for changes in speed of the turbine. Adjusting the frequency and phase requires an AC to DC to AC converter. This is usually constructed from very large IGBT semiconductors. The converter is bidirectional, and can pass power in either direction. Power can flow from this winding as well as from the output winding

dry type distribution transformer

Dry-type transformers, also known as cast resin transformers, are power transformers with windings encased in epoxy resin. This makes the installation process easier because they are dry and do not require cooling oil. ... Transformers are used to increase or decrease voltages and currents in an electrical circuit. looks like this when in case: https://bit.ly/2OLv4E7

Electroplating

Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. The term is also used for electrical oxidation of anions on to a solid substrate, as in the formation of silver chloride on silver wire to make silver/silver-chloride electrodes. Electroplating is primarily used to change the surface properties of an object (such as abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities), but may also be used to build up thickness on undersized parts or to form objects by electroforming. The process used in electroplating is called electrodeposition. It is analogous to a concentration cell acting in reverse. The part to be plated is the cathode of the circuit. In one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that it comprises and allowing them to dissolve in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they "plate out" onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated and thus the ions in the electrolyte bath are continuously replenished by the anode. Other electroplating processes may use a non-consumable anode such as lead or carbon. In these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution.[2] The most common form of electroplating is used for creating coins, such as US pennies, which are made of zinc covered in a layer of copper. Electropolishing, a process that uses an electric current to remove metal cations from the surface of a metal object, may be thought of as the opposite of electroplating.

humidity relation to static electricity

Environmental variables like relative humidity influence the level of electrostatic charges. When humidity is low, higher static charges are generated (see Table I). ... Increasing humidity to 60% limits static build-up because surface moisture on materials makes a good conductor.

Manual S

Equipment sizing manual Manual S, Residential Equipment Selection, is the ANSI-recognized, national standard providing clear instruction for interpreting and applying original equipment manufacturers' (OEM) expanded performance data.

Additional terms for refrigeration oil

Esterification - the reverse of hydrolysis. It is the process in which an organic acid and alcohol are combined to form POE oil and water. Hydrolysis - decomposition of a compound by reaction with water. In the case of POE oil, it decomposes into partial esters, organic acid and alcohol in the presence of water. The degree of hydrolysis is driven by the amount of water present. The speed at which hydrolysis occurs is dependent on temperature and the acid content (acids can act as a catalyst). Hygroscopicity - the ability of the oil to absorb moisture. The most hygroscopic refrigerant oils in descending order are: PAGs, PVEs, POEs, ABs, and mineral oils Miscibility - the ability of the oil to mix with the refrigerant. Some degree of miscibility is necessary between the oil and refrigerant so that the oil can return to the compressor during system operation. Polar - a molecular structure with an uneven distribution of electron density. PAG, PVE, and POE oils have polar structures which allow them to attract water molecules. Solubility - the ability of one compound to dissolve into another. Water is soluble in various degrees with the refrigerants and refrigeration oils.

Evaporative coolers

Evaporative coolers lower the temperature of air using the principle of evaporative cooling, unlike typical air conditioning systems which use vapor-compression refrigeration or absorption refrigeration. Evaporative cooling is the conversion of liquid water into vapor using the thermal energy in the air, resulting in a lower air temperature. The energy needed to evaporate the water is taken from the air in the form of sensible heat, which affects the temperature of the air, and converted into latent heat, the energy present in the water vapor component of the air, whilst the air remains at a constant enthalpy value. This conversion of sensible heat to latent heat is known as an isenthalpic process because it occurs at a constant enthalpy value. Evaporative cooling therefore causes a drop in the temperature of air proportional to the sensible heat drop and an increase in humidity proportional to the latent heat gain. Evaporative cooling can be visualized using a psychrometric chart by finding the initial air condition and moving along a line of constant enthalpy toward a state of higher humidity. A simple example of natural evaporative cooling is perspiration, or sweat, secreted by the body, evaporation of which cools the body. The amount of heat transfer depends on the evaporation rate, however for each kilogram of water vaporized 2,257 kJ of energy (about 890 BTU per pound of pure water, at 95 °F (35 °C)) are transferred. The evaporation rate depends on the temperature and humidity of the air, which is why sweat accumulates more on humid days, as it does not evaporate fast enough. Vapor-compression refrigeration uses evaporative cooling, but the evaporated vapor is within a sealed system, and is then compressed ready to evaporate again, using energy to do so. A simple evaporative cooler's water is evaporated into the environment, and not recovered. In an interior space cooling unit, the evaporated water is introduced into the space along with the now-cooled air; in an evaporative tower the evaporated water is carried off in the airflow exhaust. Before the advent of refrigeration, evaporative cooling was used for millennia. A porous earthenware vessel would cool water by evaporation through its walls; frescoes from about 2500 BC show slaves fanning jars of water to cool rooms. A vessel could also be placed in a bowl of water, covered with a wet cloth dipping into the water, to keep milk or butter as fresh as possible.[9] Other types of phase-change cooling A closely related process, sublimation cooling, differs from evaporative cooling in that a phase transition from solid to vapor, rather than liquid to vapor, occurs. Sublimation cooling has been observed to operate on a planetary scale on the planetoid Pluto, where it has been called an anti-greenhouse effect. Another application of a phase change to cooling is the "self-refrigerating" beverage can. A separate compartment inside the can contains a desiccant and a liquid. Just before drinking, a tab is pulled so that the desiccant comes into contact with the liquid and dissolves. As it does so, it absorbs an amount of heat energy called the latent heat of fusion. Evaporative cooling works with the phase change of liquid into vapor and the latent heat of vaporization, but the self-cooling can uses a change from solid to liquid, and the latent heat of fusion, to achieve the same result.

Shaded-pole motor

Has little starting torque. The shaded-pole motor is the original type of AC single-phase induction motor, dating back to at least as early as 1890.[1] A shaded-pole motor is a small squirrel-cage motor in which the auxiliary winding is composed of a copper ring or bar surrounding a portion of each pole.[2] When single phase AC supply is given to the stator winding, due to shading provided to the poles, a rotating magnetic field is generated. This auxiliary single-turn winding is called a shading coil. Currents induced in this coil by the magnetic field create a second electrical phase by delaying the phase of magnetic flux change for that pole (a shaded pole) enough to provide a 2-phase rotating magnetic field. The direction of rotation is from the unshaded side to the shaded (ring) side of the pole.[2] Since the phase angle between the shaded and unshaded sections is small, shaded-pole motors produce only a small starting torque relative to torque at full speed. Shaded-pole motors of the asymmetrical type shown are only reversible by disassembly and flipping over the stator, though some similar looking motors have small, switch-shortable auxiliary windings of thin wire instead of thick copper bars and can reverse electrically. Another method of electrical reversing involves four coils (two pairs of identical coils). The common, asymmetrical form of these motors (pictured) has only one winding, with no capacitor or starting windings/starting switch,[4] making them economical and reliable. Larger and more modern types may have multiple physical windings, though electrically only one, and a capacitor may be used. Because their starting torque is low, they are best suited to driving fans or other loads that are easily started. They may have multiple taps near one electrical end of the winding, which provides variable speed and power by selection of one tap at a time, as in ceiling fans. Moreover, they are compatible with TRIAC-based variable-speed controls, which often are used with fans. They are built in power sizes up to about 1⁄4 horsepower (190 W) output. Above 1⁄3 horsepower (250 W), they are not common, and for larger motors, other designs offer better characteristics.

heat reclaim coil

Heat reclaim coils (also referred to as hot gas reheat coils) take advantage of the hot gas in the compressor discharge line as a source for heat. They can be piped either in parallel or in series with the normal condenser.

high gain

High-gain antennas are focused antennas with narrow radio beams, allowing for precise targeting of radio signals. Precise; small band gap

HFO refrigerant

Hydrofluoroolefins (HFOs) are unsaturated organic compounds composed of hydrogen, fluorine and carbon. These organofluorine compound are of interest as refrigerants. Unlike traditional hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), which are saturated, HFOs are olefins, otherwise known as alkenes. HFO refrigerants are categorized as having zero ozone depletion potential (ODP) and low global warming potential (GWP) and so offer a more environmentally friendly alternative to CFCs, HCFCs, and HFCs. Many refrigerants in the HFO class is inherently stable chemically and inert, non toxic, and non-flammable or mildly flammable. Many HFOs have the proper freezing and boiling points to be useful for refrigeration at common temperatures. They also show promise as blowing agents, i.e. in production of insulation foams, food industry, construction materials, and others. HFOs are being developed as "fourth generation" refrigerants with 0.1% of the GWP of HFCs. 2,3,3,3-Tetrafluoropropene, HFO-1234yf, is a hydrofluoroolefin (HFO) with the formula CH2=CFCF3. It is also designated R-1234yf as the first of a new class of refrigerants:[1] it is marketed under the name Opteon YF by Chemours and as Solstice YF by Honeywell.[2] HFO-1234yf has a global warming potential (GWP) of less than 1,[3][4] compared to 1,430 for R-134a[5] and 1 for carbon dioxide. This colorless gas is being used as a replacement for R-134a as a refrigerant in automobile air conditioners. As of 2018, 50% of new vehicles from "original equipment manufacturers" (OEMs) are estimated to use HFO-1234yf.[6]

capacitance hygrometer

Hygrometer uses for measuring the humidity present in the surrounding environment. The term humidity means the amount of water vapour present in the gas. The physical properties of the material changes by the effect of the humidity and this principle use in hygrometer for measurement. The absolute humidity shows the amount of water vapour presents per unit volume. And the relative humidity is the ratio of the actual water vapour pressure to the maximum water vapour pressure reaches in the substance at the particular temperature. The relative humidity depends on the temperature. Capacitive Hygrometer The change in capacitance of the capacitor shows the surrounding humidity. The capacitive hygrometer gives the very accurate result. It is made by placing the hygroscopic material between the metal electrodes. The hygroscopic material can quickly absorb the water. The material absorbs water because of which the capacitance of the capacitor decreases. The electronic circuit measures the change in capacitance. Resistive Hygrometer The conducting film of the resistive hygrometer is made by the lithium chloride and the carbon. The conducting film places between the metal electrodes. The resistance of the conducting film varies with the change in the value of humidity present in the surrounding air. The moisture absorbs by the lithium chloride will depend on the relative humidity. If the relative humidity is high, the lithium chloride will absorb more moisture and their resistance decreases. The change in the value of resistance is measured by applying the alternating current to the bridge. The direct current is not used in the bridge as they breakdowns the layer of lithium chloride. The obstructions occur in the flows of current shows the value of resistance or the value of relative humidity. https://circuitglobe.com/hygrometer.html

hyperbolic cooling towers

Hyperboloid (sometimes incorrectly known as hyperbolic) cooling towers have become the design standard for all natural-draft cooling towers because of their structural strength and minimum usage of material. The hyperboloid shape also aids in accelerating the upward convective air flow, improving cooling efficiency.

Curie temperature

In physics and materials science, the Curie temperature (TC), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Curie temperature is named after Pierre Curie, who showed that magnetism was lost at a critical temperature. The force of magnetism is determined by the magnetic moment, a dipole moment within an atom which originates from the angular momentum and spin of electrons. Materials have different structures of intrinsic magnetic moments that depend on temperature; the Curie temperature is the critical point at which a material's intrinsic magnetic moments change direction. Permanent magnetism is caused by the alignment of magnetic moments and induced magnetism is created when disordered magnetic moments are forced to align in an applied magnetic field. For example, the ordered magnetic moments (ferromagnetic, Figure 1) change and become disordered (paramagnetic, Figure 2) at the Curie temperature. Higher temperatures make magnets weaker, as spontaneous magnetism only occurs below the Curie temperature. Magnetic susceptibility above the Curie temperature can be calculated from the Curie-Weiss law, which is derived from Curie's law. In analogy to ferromagnetic and paramagnetic materials, the Curie temperature can also be used to describe the phase transition between ferroelectricity and paraelectricity. In this context, the order parameter is the electric polarization that goes from a finite value to zero when the temperature is increased above the Curie temperature.

Superheating

In physics, superheating (sometimes referred to as boiling retardation, or boiling delay) is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling. This is a so-called metastable state or metastate, where boiling might occur at any time, induced by external or internal effects.[1][2] Superheating is achieved by heating a homogeneous substance in a clean container, free of nucleation sites, while taking care not to disturb the liquid. Water is said to "boil" when bubbles of water vapor grow without bound, bursting at the surface. For a vapor bubble to expand, the temperature must be high enough that the vapor pressure exceeds the ambient pressure (the atmospheric pressure, primarily). Below that temperature, a water vapor bubble will shrink and vanish. Superheating is an exception to this simple rule; a liquid is sometimes observed not to boil even though its vapor pressure does exceed the ambient pressure. The cause is an additional force, the surface tension, which suppresses the growth of bubbles. Surface tension makes the bubble act like a rubber balloon (more precisely, one that is under-inflated so that the rubber is still elastic). The pressure inside is raised slightly by the "skin" attempting to contract. For the bubble to expand, the temperature must be raised slightly above the boiling point to generate enough vapor pressure to overcome both surface tension and ambient pressure. What makes superheating so explosive is that a larger bubble is easier to inflate than a small one; just as when blowing up a balloon, the hardest part is getting started. It turns out the excess pressure due to surface tension is inversely proportional to the diameter of the bubble.[4] This means if the largest bubbles in a container are only a few micrometres in diameter, overcoming the surface tension may require exceeding the boiling point by several degrees Celsius. Once a bubble does begin to grow, the pressure due to the surface tension reduces, so it expands explosively. In practice, most containers have scratches or other imperfections which trap pockets of air that provide starting bubbles. But a container of liquid with only microscopic bubbles can superheat dramatically. Superheating can occur when an undisturbed container of water is heated in a microwave oven. At the time the container is removed, the lack of nucleation sites prevents boiling, leaving the surface calm. However, once the water is disturbed, some of it violently flashes to steam, potentially spraying boiling water out of the container.[5] The boiling can be triggered by jostling the cup, inserting a stirring device, or adding a substance like instant coffee or sugar. The chance of superheating is greater with smooth containers, because scratches or chips can house small pockets of air, which serve as nucleation points. Superheating is more likely after repeated heating and cooling cycles of an undisturbed container, as when a forgotten coffee cup is re-heated without being removed from a microwave oven. This is due to heating cycles releasing dissolved gases such as oxygen and nitrogen from the solvent. There are ways to prevent superheating in a microwave oven, such as putting an ice popstick in the glass or using a scratched container.

Critical point (thermodynamics)

In thermodynamics, a critical point (or critical state) is the end point of a phase equilibrium curve. The most prominent example is the liquid-vapor critical point, the end point of the pressure-temperature curve that designates conditions under which a liquid and its vapor can coexist. At higher temperatures, the gas cannot be liquefied by pressure alone. At the critical point, defined by a critical temperature Tc and a critical pressure pc, phase boundaries vanish. Other examples include the liquid-liquid critical points in mixtures. For simplicity and clarity, the generic notion of critical point is best introduced by discussing a specific example, the liquid-vapor critical point. This was the first critical point to be discovered, and it is still the best known and most studied one. The figure to the right shows the schematic PT diagram of a pure substance (as opposed to mixtures, which have additional state variables and richer phase diagrams, discussed below). The commonly known phases solid, liquid and vapor are separated by phase boundaries, i.e. pressure-temperature combinations where two phases can coexist. At the triple point, all three phases can coexist. However, the liquid-vapor boundary terminates in an endpoint at some critical temperature Tc and critical pressure pc. This is the critical point. In water, the critical point occurs at around 647 K (374 °C or 705 °F) and 22.064 MPa (3200 psia or 218 atm). In the vicinity of the critical point, the physical properties of the liquid and the vapor change dramatically, with both phases becoming ever more similar. For instance, liquid water under normal conditions is nearly incompressible, has a low thermal expansion coefficient, has a high dielectric constant, and is an excellent solvent for electrolytes. Near the critical point, all these properties change into the exact opposite: water becomes compressible, expandable, a poor dielectric, a bad solvent for electrolytes, and prefers to mix with nonpolar gases and organic molecules. At the critical point, only one phase exists. The heat of vaporization is zero. There is a stationary inflection point in the constant-temperature line (critical isotherm) on a PV diagram. This means that at the critical point. Above the critical point there exists a state of matter that is continuously connected with (can be transformed without phase transition into) both the liquid and the gaseous state. It is called supercritical fluid. The common textbook knowledge that all distinction between liquid and vapor disappears beyond the critical point has been challenged by Fisher and Widom[7] who identified a p,T-line that separates states with different asymptotic statistical properties (Fisher-Widom line).

Synchronous motor

Operates at a constant speed up to full load The rotor speed is equal to the speed of the rotating magnetic field of the stator; there is no slip. Often used where the exact speed of a motor must be maintained Example: Timing such as time keeping, (clocks) A synchronous electric motor is an AC motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles. Synchronous motors contain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line current. The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field of any AC motor. A synchronous motor is termed doubly fed if it is supplied with independently excited multiphase AC electromagnets on both the rotor and stator. The synchronous motor and induction motor are the most widely used types of AC motor. The difference between the two types is that the synchronous motor rotates at a rate locked to the line frequency since it does not rely on current induction to produce the rotor's magnetic field. By contrast, the induction motor requires slip: the rotor must rotate slightly slower than the AC alternations in order to induce current in the rotor winding. Small synchronous motors are used in timing applications such as in synchronous clocks, timers in appliances, tape recorders and precision servomechanisms in which the motor must operate at a precise speed; speed accuracy is that of the power line frequency, which is carefully controlled in large interconnected grid systems. Synchronous motors are available in self-excited sub-fractional horsepower sizes to high power industrial sizes. In the fractional horsepower range, most synchronous motors are used where precise constant speed is required. These machines are commonly used in analog electric clocks, timers and other devices where correct time is required. In higher power industrial sizes, the synchronous motor provides two important functions. First, it is a highly efficient means of converting AC energy to work. Second, it can operate at leading or unity power factor and thereby provide power-factor correction.

What are the applications of a super critical boiler?

Other than Central Station Power Plants, no takers for super-critical boilers, not even Nuclear Power Stations. Only reason in favour, is the increased (theoretical)thermal efficiency and compact radiant burners, considered sufficient to offset increased cost of layout (convection heat transfer rates are poor, higher operating temperature of boiler tubes, high pressure feed pumps etc.) A supercritical steam boiler is any boiler where the pressure of the steam produced by the boiler is above 22.2MPa (3212Psi). They are being used today in many applications where there is a significant need for improved efficiency. Supercritical steam system are upward of 3.5% more efficient than sub-critical steam systems. This increase in efficiency translates into a 8% improvement in air quality. Supercritical steam is characterized by the elimination the phase change between liquid and gaseous state. There is only a slow increase in pressure as the total heat content of the water goes up. At supercritical pressures, steam turbine efficiency improves significantly compared to the typical subcritical cycle. Ultra-supercritical steam conditions provide even greater efficiency improvements. The combination of utilizing supercritical throttle pressures along with an increase in throttle temperatures results in cost reductions in fuel usage and handling, flue gas treatment and ash disposal. B&W's supercritical and ultra-supercritical boilers are designed to take full advantage of variable pressure turbine operation. Subcritical - up to 705 °F (374 °C) and 3,208 psi (221.2 bar) (the critical point of water) Supercritical - up to the 1,000-1,050 °F (538-566 °C); turbine speed increases dramatically, requires advanced materials Ultra-supercritical - up to 1,400 °F (760 °C) and pressure levels of 5,000 psi (340 bar) (additional innovations, not specified, would allow even more efficiency) India's first USC coal plant commissioned Sep 2019 runs at 600 °C and pressure of 270 kg/cm2 (264.8 bar) and 41.5% generation efficiency or 3.3% more than existing conventional fleet. https://www.babcock.com/-/media/documents/products/supercritical-boiler/e101-3185-supercritical-steam-generation.ashx

Supersaturation

Presence of a salt in a higher concentration than the volume able to dissolve the salt Supersaturation is a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances. It can also refer to a vapor of a compound that has a higher (partial) pressure than the vapor pressure of that compound. Special conditions need to be met in order to generate a supersaturated solution. One of the easiest ways to do this relies on the temperature dependence of solubility. As a general rule, the more heat is added to a system, the more soluble a substance becomes. (There are exceptions where the opposite is true). Therefore, at high temperatures, more solute can be dissolved than at lower temperatures. If this solution were to be suddenly cooled at a rate faster than the rate of precipitation, the solution will become supersaturated until the solute precipitates to the temperature-determined saturation point. The precipitation or crystallization of the solute takes longer than the actual cooling time because the molecules need to meet up and form the precipitate without being knocked apart by the solvent. Thus, the larger the molecule, the longer the solute will take to crystallize due to the principles of Brownian motion. The condition of supersaturation does not necessarily have to be reached through the manipulation of heat. The ideal gas law PV=nRT suggests that pressure and volume can also be changed to force a system into a supersaturated state. If the volume of solvent is decreased, the concentration of the solute can be above the saturation point and thus create a supersaturated solution. The decrease in volume is most commonly generated through evaporation. Similarly, an increase in pressure can drive a solution to a supersaturated state. All three of these mechanisms rely on the fact that the conditions of the solution can be changed quicker than the solute can precipitate or crystallize out.

Fixing Water Hammer

Pressure is used to move water through the pipes in your home. When you turn off a faucet, this pressure is no longer needed. But, it still needs to go somewhere. So what usually happens is a device called a water hammer arrestor is used to dispel the pressure from the pipe and dissipate into the air. When the water hammer arrestor isn't working (or if you don't have one), this pressure travels back down the line when you turn off the faucet. Amazingly, the shock waves from the pressure travel faster than the speed of sound and for a brief moment exert a large amount of force on the pipes. This won't damage the pipe if it just happens once, but over time it can loosen pipe joints, valves, and cause damage to the pipe. Turn off the water to your house at the main water valve. Open the faucet at the lowest point in your home, then open up faucets at high locations such as a second story bathroom. Let the low faucet drain until nothing comes out. Close the faucets and turn the water main back on. Now run the water. For a few minutes it will sputter because there's air in the lines, but once the air gets out, turn the water off. If the sound is gone, you need to get your water hammer arrestor fixed.

what refrigerants are in R-410a?

R-32 and R-125 R-410A is a near-azeotropic mixture of difluoromethane (CH2F2, called R-32) and pentafluoroethane (C2HF5, called R-125), which is used as a refrigerant in air conditioning applications. Unlike many haloalkane refrigerants it does not contribute to ozone depletion, and is therefore widely used. 410a is a HFC

R458A

R22 Retrofit Solution

R-32

R32 refrigerant is also known as difluoromethane and belongs to the HFC family of refrigerant. This gas is poised to replace the other gaseous such as R-410A and R-407C. Its chemical formula is CH2F2. GWP of 675

multi port burner

Raised Port Multi-Ring Burner in image

regen drive

Regenerative DC drives are often called "regen drives" for short. In its basic form, a regenerative braking system recovers energy by slowing the motor, and then it actually recycles the energy. used on elevators

Liquid-liquid critical point (LLCV)

The liquid-liquid critical point of a solution, which occurs at the critical solution temperature, occurs at the limit of the two-phase region of the phase diagram. In other words, it is the point at which an infinitesimal change in some thermodynamic variable (such as temperature or pressure) will lead to separation of the mixture into two distinct liquid phases, as shown in the polymer-solvent phase diagram to the right. Two types of liquid-liquid critical points are the upper critical solution temperature (UCST), which is the hottest point at which cooling will induce phase separation, and the lower critical solution temperature (LCST), which is the coldest point at which heating will induce phase separation. A liquid-liquid critical point (or LLCP) is the endpoint of a liquid-liquid phase transition line (LLPT); it is a critical point where two types of local structures coexist at the exact ratio of unity. This hypothesis was first developed by H. Eugene Stanley[1] to obtain a quantitative understanding of the huge number of anomalies present in water. Near a liquid-liquid critical point, there is always a mixture of two alternative local structures. For instance, in supercooled water, two types of local structures exist, a low-density liquid (LDL) and a high-density liquid (HDL), so above the critical pressure, a higher percentage of HDL exists while below the critical pressure a higher percentage of LDL is present. The ratio r = LDL/(LDL + HDL) of phase amounts[clarification needed] is determined according to the thermodynamic equilibrium of the system, which is often governed by external variables such as pressure and temperature.[3] A discontinuity is present in r when crossing the liquid-liquid phase transition, which separates the LDL-rich phase from the LDL-poor phase. At any point of the liquid-liquid phase transition, including the associated liquid-liquid critical point, the ratio of LDL to HDL is exactly one (r = ½). The liquid-liquid critical point theory can be applied to all liquids that possess the tetrahedral symmetry. The study of liquid-liquid critical points is an active research area with hundreds of papers having been published, though only a few of these investigations have been experimental since most modern probing techniques are not fast and/or sensitive enough to study them.

Sensible Heat Ratio (SHR)

The ratio of sensible heat to enthalpy (total heat). sensible heat / (sensible + latent)

Why would water backflow?

The reason is due to the serious consequences of failure of the valve or more likely the individuals who are likely to devise ways to circumvent its purpose, which is to protect you and your fellow citizens from the contamination of the water supply by boiler additives, chemicals, and contaminants of many other types. The regular checking is designed more to catch these "crafty" ways of circumventing needed safety measures than to ensure the quality of the device itself. Additionally, some of these devices are less than optimal, as politics have dictated that lower-cost and therefore less reliable devices can be and are used. Finally, as most people know, things happen with plumbing devices, such as scale build-up, disintegrated seals, and so on. In short, it is mostly to catch stupid things done by non-plumbers that endanger the water supply. Most people lack the insight to realize water sometimes flows in unexpected ways, but always from high to low pressure, so sometimes your boiler is at a higher pressure than your incoming water feed, and your back flow can kill your neighbors or make them seriously ill. The risk is not entirely yours. This is why we use RPZ's.

Universal motor

The universal motor is a type of electric motor that can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field.[1] It is a commutated series-wound motor where the stator's field coils are connected in series with the rotor windings through a commutator. It is often referred to as an AC series motor. The universal motor is very similar to a DC series motor in construction, but is modified slightly to allow the motor to operate properly on AC power. This type of electric motor can operate well on AC because the current in both the field coils and the armature (and the resultant magnetic fields) will alternate (reverse polarity) synchronously with the supply. Hence the resulting mechanical force will occur in a consistent direction of rotation, independent of the direction of applied voltage, but determined by the commutator and polarity of the field coils. Universal motors have high starting torque, can run at high speed, and are lightweight and compact. They are commonly used in portable power tools and equipment, as well as many household appliances. They're also relatively easy to control, electromechanically using tapped coils, or electronically. However, the commutator has brushes that wear, so they are much less often used for equipment that is in continuous use. In addition, partly because of the commutator, universal motors are typically very noisy, both acoustically and electromagnetically. A negative aspect is the maintenance and short life problems caused by the commutator, as well as electromagnetic interference (EMI) issues due to any sparking. Because of the relatively high maintenance commutator brushes, universal motors are best-suited for devices such as food mixers and power tools which are used only intermittently, and often have high starting-torque demands. Another negative aspect is that these motors may only be used where mostly-clean air is present at all times. Due to the dramatically increased risk of overheating, totally-enclosed fan cooled universal motors would be impractical, though some have been made. Such a motor would need a large fan to circulate enough air, decreasing efficiency since the motor must use more energy to cool itself. The impracticality comes from the resulting size, weight, and thermal management issues which open motors have none of.

wind energy equation

The wind power increases with the cube of the wind speed. In other words: doubling the wind speed gives eight times the wind power. ... Therefore, wind farms in the prevailing wind direction need a minimum distance of eight times the rotor diameter.

different types of chillers

There are three different types of chillers:(1) air, (2) water, and (3) evaporative condensed chiller. There are four subcategories in each of the above categories for industrial chillers: (1) reciprocating, (2) centrifugal, (3) screw driven (4) and absorption chillers.

Why does coffee only make a stain on the mug at the level of the coffee?

There are two effects occurring here: Your liquid is evaporating, and There is a capillary effect due to the adhesive property of water that lets water cling onto the side of your mug. It's the same effect that makes a meniscus. So these two effects combined actually drives a current in your solution that brings these suspended particles to the cup, at the level of the coffee (i.e., the contact line), and the particles are deposited there when the water evaporates. When seen in a droplet evaporating on a surface, this is also known as the coffee ring effect, and is frequently cited in literature because it can separate particles based on particle size as well, so can be used in nano-scale chromatography such as separating proteins, micro-organisms, and mammalian cells. https://www.reddit.com/r/askscience/comments/24uobk/why_does_coffee_only_make_a_stain_on_the_mug_at/chav96m?utm_source=share&utm_medium=web2x

Should HRV run continuously?

Therefore, the HRV should be shut off in warm weather, not cold, contrary to what your HVAC source has told you. ... If the HRV is running constantly, year-round, it's bringing in too much warm, moist air in the summer and too much cold air in the dead of winter, causing the furnace to run constantly.

How much moisture do people generate per hour?

These are 0.2 pounds of water per hour for a person at rest, 0.6 pounds of water per hour for a person at hard work, and 0.4 pounds of water per hour produced by a person indoors on average.

transceiver

a device that can both transmit and receive communications, in particular a combined radio transmitter and receiver.

ideal gas

a hypothetical gas whose molecules occupy negligible space and have no interactions, and which consequently obeys the gas laws exactly. An ideal gas is a theoretical gas composed of many randomly moving point particles whose only interactions are perfectly elastic collisions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.

R513A

a low Global Warming Potential (GWP) HFO refrigerant blend. Substitute for R134a, with comparable physical and thermodynamic properties Azeotropic refrigerant blend containing R1234yf and R134a Refrigerant must be charged from the liquid phase to ensure accurate composition Low GWP of 631, 56% reductions compared to R134a

Isochoric process

a process that takes place at a constant volume An isochoric process, also called a constant-volume process, an isovolumetric process, or an isometric process, is a thermodynamic process during which the volume of the closed system undergoing such a process remains constant. An isochoric process is exemplified by the heating or the cooling of the contents of a sealed, inelastic container: The thermodynamic process is the addition or removal of heat; the isolation of the contents of the container establishes the closed system; and the inability of the container to deform imposes the constant-volume condition. The isochoric process here should be a quasi-static process.

Isothermal process

a thermodynamic process that takes place at constant temperature

paint markers

allow you to write on any surface

desoldering gun

can be used to take out components on a circuit board and resolder new ones in

Isenthalpic process

constant enthalpy A process in which enthalpy of first and last state is same. That is enthalpy remains constant. Obviously a process must have zero net heat/work transfer to be isenthalpic. Free expansion is an example of isenthalpic process.

Isentropic process

entropy remains constant In thermodynamics, an isentropic process is an idealized thermodynamic process that is both adiabatic and reversible. The work transfers of the system are frictionless, and there is no transfer of heat or matter. Such an idealized process is useful in engineering as a model of and basis of comparison for real processes. The word "isentropic" is occasionally, though not customarily, interpreted in another way, reading it as if its meaning were deducible from its etymology. This is contrary to its original and customarily used definition. In this occasional reading, it means a process in which the entropy of the system remains unchanged. For example, this could occur in a system where the work done on the system includes friction internal to the system, and heat is withdrawn from the system in just the right amount to compensate for the internal friction, so as to leave the entropy unchanged.

Spray pond

is a pond where warm water is sprayed into the air and is cooled by the air as it falls into the pond. Spray ponds require 25 to 50 times the area of a cooling tower because water loss due to air drift is high. A spray pond is a reservoir in which warmed water (e.g. from a power plant) is cooled before reuse by spraying the warm water with nozzles into the cooler air. Cooling takes place by exchange of heat with the ambient air, involving both conductive heat transfer between the water droplets and the surrounding air and evaporative cooling (which provides by far the greatest portion, typically 85 to 90%, of the total cooling). The primary purpose of spray pond design is thus to ensure an adequate degree of contacting between the hot injection water and the ambient air, so as to facilitate the process of heat transfer. The spray pond is the predecessor to the natural draft cooling tower, which is much more efficient and takes up less space but has a much higher construction cost. A spray pond requires between 25 and 50 times the area of a cooling tower. However, some spray ponds are still in use today.

Why does hot air rise?

it is less dense

tachometer

measuring instrument for indicating speed of rotation measures number of rotations an instrument which measures the working speed of an engine (especially in a road vehicle), typically in revolutions per minute. Picture: the inside of the tachometer has an infrared sensor and receiver that will detect how many times their signal is disrupted by the rotation of the motor. The infrared signal is constantly emitted so each disruption will be one rotation.

Decomposition potential

minimum energy needed for electrolysis to occur Decomposition potential or Decomposition voltage, in electrochemistry, refers to the minimum voltage between anode and cathode of an electrolytic cell that is needed for electrolysis to occur.

Bubble chamber

radiation detector, consisting of a container of superheated liquid under high pressure, that is used to detect the paths of charged particles. A bubble chamber is a vessel filled with a superheated transparent liquid (most often liquid hydrogen) used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser,[1] for which he was awarded the 1960 Nobel Prize in Physics.[2] Supposedly, Glaser was inspired by the bubbles in a glass of beer; however, in a 2006 talk, he refuted this story, although saying that while beer was not the inspiration for the bubble chamber, he did experiments using beer to fill early prototypes. While bubble chambers were extensively used in the past, they have now mostly been supplanted by wire chambers and spark chambers. Notable bubble chambers include the Big European Bubble Chamber (BEBC) and Gargamelle.