Turner rmo

Water pressure

1 foot of water = 0.433 psi 1 psi 2.31 ft of water.

Tons of cooling

1lb of ice will absorb 144 BTU's as it melts. 1 ton of ice (2000 lbs) will absorb 144 x 2000 = 288,000 BTU's. 24 hours = 288,000 BTU's a day. 60 mins = 12,000 BTU's an hour. 1 min = 200 BTU's a day.

Refrigerant type high pressure

A refrigerant which must be used in a vessel above atmospheric pressure.

Refrigerant type low pressure

A refrigerant which must be used in a vessel below atmospheric pressure. A refrigerant which must be used in a vacuum.

Types of condensers

Air-cooled condenser and water-cooled condenser

Water cooled condenser

Capable of achieving lower head pressures. Can be used on medium to large-sized machines

Non mechanical metering device

Capillary tube. Orifice plate.

Types of non positive displacement compressors

Centrifical

Air-cooled condenser

Cheaper. Less cleaning. Can be used on small to medium-sized machines

Compound gauge

Combination of a vacuum gauge and a pressure gauge. Measures vacuum in inches of mercury. Measures pressure above atmospheric in psig.

Subcooling

Cooling the liquid refrigerant below its saturation point temperature at which it is condensed 211 degrees Fahrenheit water is 1 degrees subcooled

Water-cooled condenser types

Cross flow period. parallel flow. Counterflow

Fouling water tubes

Depositing of sediment from condenser water onto condenser tubes or coil insulation. Results in less heat transfer between cooling condenser water and refrigerant. Causes high head pressure

Red litmus paper

Detects ammonia leaks. Turns blue

Nessler solution

Detects ammonia leaks. Turns yellow

bromothymol Blue

Detects carbon dioxide leaks. Turns yellow

Evaporator high side system

Discharge pressure. Condenser pressure. Head pressure

Flash gas

Evaporation of a small amount of liquid refrigerant as it passes through the metering device. Cause of liquid refrigerants temperature drop from the high temperature in the liquid line to the low temperature in the evaporator

Reciprocating system components major components

Evaporator. Compressor. Condenser. Metering device. Piping.

Evaporator function

Exchange heat between the refrigerant and the load

Disadvantages of a flooded evaporator

Far greater amount of refrigerant required. Leaks are harder to find

Heat

Form of energy. Transferred from one place to another. Can't be seen. Is measured by its effects on substances.

Frost

Frozen condensation. Frost insulates DX coils and prevents proper heat transfer. Frost can result in low suction pressure

New York City refrigerant classifications

Group one non-toxic non flammable CO2, r - 11, r - 12. Group 2 toxic ammonia. Group 3 flammable butane , Ethylene

Evaporator

Heat exchanger which absorbs heat to evaporate or boil low pressure liquid refrigerant into low-pressure vapor.

Sensible heat

Heat that can be measured with a thermometer. Change in temperature, not change in state.

Latent heat

Heat which causes a change in physical state. Solid to liquid.(fusion/melting) Liquid to vapor.(vaporization) Vapor to liquid.(condensation)

Superheat

Heating Vapor refrigerant above its saturation point temperature at which it is evaporated. 213 degrees Fahrenheit steam is one degree superheated

Ashrae refrigerant classifications

High flammability A3 , B3. Low flammability A2, B2. No flammability A1, B1.

Refrigerant qualities

How much heat does it absorb per pound. How much heat can it absorb after it passes through the metering device. Is it toxic. Is it flammable. How easy is it to detect leaks. At what temperature will it break down. At what pressures must it be used at.

1 lb of ice

Ice = 0 °F - 32°F. Water= 32 °F - 212 °F. Steam= 212 °F - 220 °F.

Automatic expansion valve disadvantages

If load increases, evaporator will starve. If load decreases, evaporator will be flooded

Tev problems

If opening force ( bulb pressure) is lost; evaporator will be starved. If closing force (spring or back pressure) is lost; evaporator will be flooded. If sending bulb insulation falls off; evaporator will be flooded. If sensing bulb is installed in wrong location; evaporator will be starved.

Low side float disadvantages

If the float is punctured the evaporator will flood. If the vapor connection is blocked it will not properly feed the evaporator

High side float disadvantages

If the float is punctured the evaporator will starve. If too much refrigerant is in the system this valve will not close flooding the evaporator

Charles law

If the temperature of a gas or vapor goes up and the gas or vapor cannot expand, the pressure will go up. If The volume of a gas or vapor is reduced the pressure and temperature will go up.

Dalton's law of partial pressures

If two separate vapors are contained in the same vessel their separate pressure will accumulate.

High head pressure

In extreme cases can cause the condenser vessel to rupture or explode. More often will cause Refrigeration machine control to turn compressor off which will leave the building with no Cooling. Can cause pressure relief valve to open which releases refrigerant outside of machine which is bad

Non positive displacement compressor

Increases the pressure of the refrigerant Vapor by rapidly accelerating then decelerating it. Also called Dynamic compression

Positive displacement compressor

Increases the pressure of the refrigerant Vapor by reducing its volume

Mechanical metering device

Manuel metering device. Low side float. High side float. Automatic expansion valve. Thermostatic expansion valve (txv).

Measuring sensible heat

Measured with thermometers Fahrenheit or celsius. Fahrenheit - 32 °F ÷ 1.8 = Celsius. Celsius × 1.8 + 32 °F = Fahrenheit.

Pressure gauge

Measures pressure above atmospheric pressure (14.7 psi). Readings are in psig instead of PSIA. Psig + 14.7 psi = PSIA.

Barometer

Measures pressure in inches of mercury.

Pressure gauge

Measures pressure in pounds per square inch.

Starving the evaporator

Metering device sending inadequate amount of refrigerant to the evaporator to cool load

Flooding the evaporator

Metering device sending too much refrigerant to the evaporator endangering the compressor float comparison.

Feeding the evaporator

Metering device supplying liquid refrigerant to the evaporator in response to the load

Feeding the evaporator

Metering device supplying low pressure liquid refrigerant to the evaporator in response to the load. The load increases if there is more refrigerant sent to the evaporator. Low decreases if there is less refrigerant sent to the evaporator

Low side system

Metering device to Inlet of compressor. Suction pressure. Evaporator pressure. Back pressure.

Humidity

Moisture in ambient air. Air temperature determines the amount of moisture it can hold. Warmer air holds more moisture colder air holds less

Condensation

Moisture that has condensed from ambient air

Condenser Water Supplies

Natural bodies of water which are rivers lakes Wells and water regulating valve. Recirculated water. Cooling towers in water recirculating condensers

Refrigerant safety

Never handle refrigerant or equipment with bare hands. Always make sure equipment is leak checked. Toxic or flammable refrigerants can be detected by a refrigerant monitor. Machine rooms must have mechanical ventilation which removes refrigerant paper if there is a leak.

Halide torch

No leak turns blue. Small leak turns green. Big leak turns dark blue. Restriction inline turns yellow

Two types of metering device

Non mechanical and mechanical

Dry type evaporator

Only contains enough refrigerant to satisfy the load. When the load increases more refrigerant is needed. When the load decreases less refrigerant is needed. Example direct expansion DX coil

Thermostatic expansion valve

Opening force = bulb pressure. Closing force = spring pressure. Closing force = evaporator pressure

Automatic expansion valve (constant pressure valve)

Opening force = spring pressure. Closing force = evaporator pressure

High side system

Outlet of compressor to Inlet of metering device. Discharge pressure. Condenser pressure. Head pressure.

Chapter 2

Pressure

Engineer tools

Pressure / temperature conversion chart. Standard ton conditions chart. Refrigerant classifications.

Vacuum

Pressure inside vessel which is below atmospheric pressure. Pressure below 14.7 PSIA.

Barometric pressure

Pressure measured with a barometer. Also an absolute pressure. 1 hg barometric = 0.491 psia. 1 psi = 2 hg barometric.

Atmospheric pressure

Pressure of the air around us. Equal to 14.7 pounds per square inch(psi) at sea level. Equal to 29.92 inches of mercury(30hg).

Absolute pressure

Pressure which starts at 0

Types of positive displacement compressor

Reciprocated. Rotary. Screw. Scroll

Indirect refrigeration system

Refrigerant in the evaporator coils a secondary refrigerant such as chilled water or brine which then cools the load. Disadvantages. Requires more system components and piping

Direct refrigeration system

Refrigerant in the evaporator coils the load directly. Direct expansion coil DX coil. Disadvantages. Far greater health hazard when leaking

Horizontal Shell & tube evaporators

Refrigerant is in the shell chilled water is in the tubes. Liquid enters the bottom Vapor exits the top. Eliminators prevent liquid from entering compressor. Chilled water return from building is usually 55 degrees Fahrenheit. Chilled water supply to building is usually 45 degrees Fahrenheit

Compressor function

Remove Vapor refrigerant from the evaporator. Maintain the pressure on the low side of the system so that refrigerant in the evaporator can boil at a low temperature. Maintain the pressure on the high side of the system so that the refrigerant in the condenser can condense at a high temperature

Condenser function

Remove the heat of compression added by the compressor

Lower head pressure

Results in less pressure differential which is the difference between high and low side of machine. Low pressure differential will cause an adequate amount of liquid to be supplied to low side of machine which is the evaporator

Three types of direct expansion coils

Single row coil Multi-role coil. Finned multi-role coil

Evaporator low side system

Suction pressure. Evaporator pressure. Back pressure

Saturation point

Temperature at which a liquid or vapor will change state. Water boils at 212 °F at atmospheric pressure (14.7 PSIA). Water will boil at a higher temperature if The pressure is greater than 14.7 PSIA. Water in a pressure cooker boils at temperatures above 212 °F due to the higher pressure.

Condenser

The heat exchanger in which the removal of heat causes high pressure Vapor to condense and liquify into a high pressure liquid

Dew point

The temperature below which moisture in ambient air will condense. Cold DX coils dehumidify and remove moisture from ambient air

Refrigeration

Transfer of heat. Heat is removed from load. Heat is transferred to a space.

Btu

Unit of measuring heat. Amount of heat that will change the temperature of 1 pound of water 1 degree Fahrenheit.

Water regulating valve

Used to maintain a constant head pressure. Used when the condenser water is taken from a natural water supply such as Lake Pond or well when a constant water temperature is unattainable. Varies amount of water and response to head pressure

Vacuum gauge

Vacuum to PSIA: vaccum - 30 = PSIA. Reads like barometer in reverse

Flooding the evaporator

When a metering device said too much refrigerant to the evaporator for the load to boil. Can be caused by the metering device being stuck open

Starving the evaporator

When a metering device sends too little refrigerant to the evaporator to cool load. Can be caused by restriction blocking flow through the metering device or liquid line

Saturated

When a substance while changing State exist as both liquid and vapor. Water boiling at 212 degrees Fahrenheit is saturated

Disadvantages of dry evaporators

When flooded there is a high risk of liquid refrigerant entering the compressor. Far lower cooling capacity

Liquid seal

When the level of liquid refrigerant in the condenser or receiver is high enough to ensure that only high pressure liquid is entering the liquid line

Loss of liquid seal

When the level of liquid refrigerant is in the condenser or receiver to allow high-pressure Vapor to enter the liquid line

How cooling tower works

971 pounds of 90 degrees Fahrenheit water are sprayed into the cooling tower. One pound of water evaporate which absorbs 970 BTU's here another 1 BTU per pound is 1 degree Fahrenheit when the water leaves the cooling tower it is 89 degrees Fahrenheit

How cooling tower works again

98 pounds of 90 degree Fahrenheit water are sprayed into the cooling tower. One pound of water evaporates which absorbed 970 BTU's. 970 BTUs divided by 97 pounds equals 10 BTU's per pound 10 BTUs per pound equals 10 degrees Fahrenheit temperature drop. Water leaves the cooling tower at 80 degrees

Refrigerant

A fluid which is used for the transfer of heat inside a refrigeration machine. Most refrigerants behave similarly to water in that: They have a freezing and boiling point. They're boiling point changes depending on the pressure applied to it.

Pressure

A force which is applied to a surface or object.

Flooded type evaporators

Always contains a large amount of liquid refrigerant regardless of load. As the load increases more liquid is boiled. As the load decreases less liquid is boiled. Example horizontal Shell & tube evaporator

Latent heat of evaporation

Amount of BTU's a pound of liquid refrigerant can absorb while evaporating.

Refrigerating effect

Amount of BTU's a pound of refrigerant can absorb after passing through the metering device.

Specific heat

Amount of BTU's needed to change to temp of 1 lb of water to 1 °F. Specific heat of water = 1. Specific heat of ice =0.5. Specific heat of steam = .5

Restriction

An obstruction which slows the flow of fluid. Restricting the flow of liquid refrigerant causes a decrease in pressure.

High side float

Attached to condenser. Supplies more refrigerant as it is liquefied in the condenser

Low side float

Attached to the evaporator. Supplies more refrigerant as it is boiled in the evaporator.

Metering device

The component which returns the high pressure/high temperature liquid to a low pressure/low temperature liquid for reuse in the evaporator.