Test 1: Power points 1-8
Emittance
() The ratio of radiant energy emitted by a material to a blackbody at the same temperature.
British thermal unit
(Btu) a-measure of thermal energy (heat); quantity of energy required to raise the temperature of one pound of water by one degree Fahrenheit.
British thermal unit
(Btu) a-measure of thermal energy (heat); quantity of energy required to raise the temperature of one pound of water by one degree Fahrenheit. 1 Btu = 1055.1 Joules = 252 calories = .252 kilocalories = 778 ft-lb = .293 Watt-hr
A Btu is a measure of energy Calorie (cal) = the amount of heat needed to raise 1 gram (g) of water 1°C Kilocalorie (kcal) = the amount of heat needed to raise 1 kilogram (kg) of water 1°C (the term "calorie" as applied to diet is actually kcal.)
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Absorbance (α) is the property that quantifies how well a material absorbs radiation.
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Air near surfaces heats and cools. Warm air rises and cool air drops. Shear and pressure differences cause eddies to form.
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Diffusion is more rapid when either the conductivity is high or the specific heat is low.
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Emittance (ε) is the property that quantifies how well a material emits radiation.
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Emittance ε is the ratio of a surface's radiant emission (and absorption) divided by theoretical black-body radiant emission (and absorption) at a particular wavelength or range of wavelengths.
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For example, glass is transparent in part of UV, the visible, and the near IR, but opaque in the far IR range. A black plastic trash bag is opaque in the visible range, but semi-transparent in far IR.
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Heat Diffusion in Earth shows the effects of diffusion when the very large thermal mass of soil can delay the onset of external temperatures on interior, earth-sheltered spaces.
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Notes
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The Thermal Capacitance (CAP) of water = ρ × c = 62.5lb/ft³ × 1.00Btu/lb/°F = 62.5 Btu/ft³ per °F.
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The Thermal Capacity of this 1 cu. ft. cube = M × c = 62.5lb × 1.00Btu/lb/°F = 62.5 Btu per °F of temperature change. Since architects work in terms of volume (V) more than mass (M), capacity calculations using volume are more convenient. Water density = 62.5 lb/ ft³ Density = ρ lb/ft³.
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The Thermal Capacity of this cube = CAP × V = 62.5Btu/ft³ × 1.00ft³ = 62.5 Btu per °F
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The example showing temperature distributions in a massive wall uses design and the temperature range of Reno NV, to illustrate how a thermally massive wall, such as, adobe or concrete can moderate interior temperatures. The importance of nighttime cooling ventilation also has an impact in this model.
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The examples compare a light wood frame wall with a massive brick wall. Frame walls often have low thermal mass, but excellent resistance to conduction. The brick wall conducts heat rapidly, but shows a smaller change of temperature due to its great thermal capacity.
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Values range from 0 to 1. At any given wavelength absorbance = emittance
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Adiabatic Process
A process in which Enthalpy does not change.
Black Body
A theoretical object that absorbs and emits all electromagnet radiation equally.
Black Body
A theoretical object that absorbs and emits all wavelengths of electromagnetic radiation perfectly. "Black bodies" below 700 K +/- (427 ºC, 800ºF) produce infrared and other long-wave energy, but little radiation at visible wavelengths. At higher temperatures, more and a larger range of electromagnetic radiation, (including visible light) is produced. As the temperature increases, ultraviolet and shorter-wavelength radiation is produced in larger amounts.
Heat
A type of energy. Energy that raises the temperature of objects. Objects are hot because of heat. Objects are cold due to a lack of heat. Stored in or released from materials " " " " " chemical reactions. Conduction, Radiation, Mass Transport, Convection, circulation," " " " " phase changes of materials converted to or from mechanical energy " " " " electromagnetic radiation moved from one place to another through ventilation, etc.
MET
A unit of metabolic heat generation = 50 kcal/(h×m²) = 18.4 Btu/(h×ft²)
Radiant Heat Loss
All objects in a normal space are radiating significant amounts of radiant energy. Most of this radiation is in the infrared range - Some is in the visible range (light fixtures). People also radiate significant amounts of radiant energy. With average conditions, people radiate the same amount of energy as a 100 Watt light bulb, but almost entirely in the infrared range.
HVAC
Boilers and chillers are noisy, so they are usually in basements or ground level rooms. Cooling towers are also noisy, but are usually on roofs or in top story enclosures because of the heat and steam/mist plume they generate. Packaged units combine boiler, chiller, and air handler into one unit. An integral condenser can take the place of a cooling tower, or a separate cooling tower may be used. In building complexes or larger buildings, a separate building or enclosure makes sense. Equipment rooms for boilers andchillers may be separate or combined. Multiple boilers and chillers may have greater initial cost, but will operate more efficiently, and allow for more flexibility for repairs. Flues for gas or oil fired boilers must extend vertically through building. Equipment rooms are usually longer than they are wide.
Btu/h or Btuh -
British thermal units per hour
Metabolism
Comfort is greatly affected by the metabolic level induced by activity. The MET unit wasdeveloped as a descriptor of metabolic heat generated. 1 MET = 50 kcal/(h×m²) = 18.4 Btu/(h×ft²)
Common Usage
E = V × CAP × ΔT | Where: E = heat Energy Btu, V = Volume ft³, CAP = Thermal Capacitance Btu/ft³/°F, ΔT = change of Temperature °F. It is often convenient to find the Thermal Capacity of all objects in a space by summing the products of Volume and Capacitance of all materials to find total thermal capacity Σ(V × CAP) Where Σ(V×CAP) = V1 × CAP1 + V2 × CAP2 + ...
The equations are then used thus
E = Σ(V×CAP) × ΔT or ΔT = E ÷ Σ(V×CAP) × or Σ(V×CAP) = E ÷ ΔT
Infrared (IR) Radiation
Electromagnetic radiation of a longer wavelength than red light.
Ultraviolet (UV) radiation
Electromagnetic radiation of a shorter wavelength than violet light. From 200nm to 400nm (nm = nanometer = billionth of a meter).
Space usage
Ext. walls 5.4%, Data 0.5%, Electric 1.9%, Duct riser 2.2%, Mech. room 6.8%, Jan. & Stor. 2.9%, Restrooms 1.8%, Elevator 0.6%, Vert. circ. 4.2%, Horiz. circ. 17.8%, Program Space 55.9% (including interior walls and structure). Floor area used for each upper floor: Mechanical riser space uses: 2.4%, Electrical or Data 1.0% Visit CoMo and study & compare exit stair design to Bond Hall.
Safety
Have two or more remote exits. Use continuous corridors & limit the length of dead end corridors to 20'. Enclosed stairs that exit directly outside.
Insolation
Heat added, per hour, from solar radiation Btu/ft²/h
Insolation
Heat added, per hour, from solar radiation Btu/ft²/h (typical values)
Air Spaces
Heat is transferred across small air spaces by: Radiation, Conduction, and to a small degree:Convection. Convection becomes a significant mechanism for additional heat transfer in larger air spaces.
HVAC
Heating, Ventilating, and Air Conditioning
Phase Change
Kinetic energy will cause an occasional molecule to change state from liquid to gas (vapor).When the molecule has left the body of liquid, part of the heat energy also leaves. Evaporation causes the body of liquid to cool.
Thermal -
Mass, Capacity, and Capacitance. When mass (M) and specific heat (c) are known, thermal capacity (M × c) may be calculated. Thermal Mass is a general term applied to Thermal Capacity and Thermal Capacitance. 1 ft³ of water = 62.5 lb
Radiant Heat Exchange
Objects within a room both emit and absorb radiant energy A person exchanges this energy with the environment. If the person's surface temperature is the same as the environment, there is no net radiant gain or loss with the person. If the environment has a warmer temperature than the person, the person experiences a net gain - if the environment is cooler, there is a net loss.
Gray Bodies
Real objects do not emit all frequencies equally. For any given wavelength: Absorbance (α) = Emittance (ε). Highly reflective materials are also poor emitters of radiation. The same material may have different properties at different wave lengths regarding: Reflection, Transmission, & Absorption and Emission.
Electrical Closets
Stacked configuration. Length of branch. Maintenance, access, and repair. Closets opening onto halls are best. Electrical closets cannot be used for storage, or located in a kitchen or restroom.
Thermal Stack
Sun heats chimney. Chimney heats air. Air expands - less dense air rises. Cool air replaces warm air. Cycle repeats and continues as long as chimney air is warmer than outside air. This principle applies to both literal and virtual thermal stack conditions.
Latent Heat of Vaporization
The amount of heat absorbed or released when a material changes state between liquid and a gas. 967 Btu / lb for water.
Thermal Mass Example
The effect of thermal mass on a passive-solar sunroom. In the mid-70s, these structures were added to both new and existing buildings, to passively collect solar energy. Overheating became a significant problem because the need for thermal mass was ignored.
Conduction
The flow of heat through materials
Conduction
The flow of heat through materials. q = u × A × ΔT Where: q Btu/h = Heat flow rate u Btu/h/ft²/°F = Conductance A ft² = Surface area ΔT °F = Temperature difference T1-T2
Conductance
The measure of a material's thermal conductive property Btu/h/ft²/°F
Convection
The movement of a fluid due to temperature differences in the fluid.
Mean Radiant Temperature
The radiant temperature of each surface times the percentage of spherical measures. Mean Radiant Temperature (MRT) is more important than air temperature for comfort. A MRT 2°C (3.6°F) higher than the air temperature provides the greatest comfort.
Diffusion
The spread of heat through an object, especially the rate of flow and the rate of local rise in temperature
Daily Range
The summer temperature range used for system design
Dew point
The temperature at which water vapor condenses from an air /water vapor mixture.
Black Body Radiation
The temperature of a black body correlates with the predominate colors emitted:100000K Blue sky, 6000K Sun, 5500K perceived white light, 2500K-3200K incandescent light bulb, 2000K Candle, 1000K dull red as in a thin wire held in a candle flame.
Thermal Spectrum
The transparency of glass and the solar spectrum at the Earth's surface more or less match. This range spans near infrared, through visible, into ultraviolet. Peak solar and peak visible also nearly match. Lower-temperature objects, such as people and the environment around us, produce little but far infrared
Ton
Ton of cooling: 12,000 Btu/h - A term for cooling ability of air conditioning equipment. This term is based on the approximate value for the amount of heat absorbed in one day, when one English ton of ice at 32ºF changes to one ton of liquid water at 32ºF. 144 Btu/lb x 2,000 lb / 24h = 12,000 Btu/h See Latent Heat of Vaporization.
Bond Hall
U-shaped corridor terminating in exit stairs. Rooftop air handler. Study & understand plans - know how your building works. Look at ventilation well on east side.
Watt-hour (W-h)
Unit of energy 1.0W-h = 3600 Joules
Watt (W)
Unit of power 1.0W = 1.0 Joule/sec
Objects
When radiant energy strikes a surface, it may be: Reflected, Transmitted, or Absorbed. The absorbed portion becomes heat, and may be emitted as longer wavelength energy. When radiant energy strikes a black body, it is: Absorbed. The absorbed portion becomes heat, and is radiated as longer wavelength energy.
Duct
a conduit for the distribution of air.
Condenser
a device designed to condense a refrigerant; an air-to-refrigerant or water-to-refrigerant heat exchanger; part of a vapor compression or absorption refrigeration cycle.
Fan
a device designed to impart energy (velocity and/or pressure to air in a supply, return, exhaust, or circulation system.
Energy
a measure of the capacity to do work.
Temperature
a measure of the density of heat in a substance.
Heating
a process that adds sensible heat to a material or space.
Cooling
a process that removes sensible and/or latent heat from a material or space.
Air conditioning
a process that simultaneously controls the temperature, moisture content, distribution, and quality of air
Packaged unit
a self-contained unit designed to provide control of air temperature, humidity, distribution, and quality.
CLO
a unit of the insulation provided by clothing. Approximately 0.15 per pound of clothing.
Math reminder
a/b/c = a/bc i.e.: Acceleration = ft/sec/sec = ft/sec²British thermal unit (Btu) is defined as: the amount of heat needed to raise the temperature of one pound of water one degree Fahrenheit.
Air handling unit
an assembly of air-conditioning components that normally includes a fan, a filter, heating and cooling coils, and control elements.
Exit arrangement
corridor terminates in exit, rarely less than two exits, sometimes three or four.
Boiler
equipment designed to heat water or generate steam.
Chiller
equipment designed to produce chilled water; see also vapor compression chiller (centrifugal, reciprocating) and absorption chiller.
Cooling tower
equipment designed to reject heat from a refrigeration cycle to the outside environment through an open cycle evaporative process; an exterior heat rejection unit in a water-cooled refrigeration system.
Near infrared
from 700nm to 3000nm (nm = nanometer = billionth of a meter). Far infrared: from 3000nm to 10000nm
Convection
heated air expands, and becomes buoyant because its new density is lower than that of the surrounding air.
CoMo
in similar buildings: 3'-6" ceiling-to-floor depth is advisable. 1'-6" or more for wall thickness. Linear corridor terminating in exit stairs. Complex plan with clear structure. Air handlers in basement. Stacked services. Extensive horizontal circulation due to multiplicity of different office. More storage needed.
Frugal Buildings
simple, compact shape, clear structure, centrally located air handler(s), fewer and larger pieces of equipment (exceptions: economy of mass production, higher energy-efficiency in residential furnaces, modular boiler and chiller systems, packaged commercial units - lower installation costs & easier to engineer,and are available on shorter notice. Stack services like plumbing, electric, and data on top of each other &fixtures that share plumbing shafts.
Cooling load
the magnitude of heat removal required to maintain a building at appropriate thermal conditions.
Efficiency
the ratio of energy output to energy input of a device or system.
Joule (J)
the standard SI unit of energy, including heat. 1 Btu = 1055.1 Joules = 252 calories = 0.252 kilocalories = 778 ft-lb = 0.293 Watt-hr 1 Therm = 100,000 Btu
Comfort Cooling, Comfort Ventilation
ventilation that aids comfort in hot climates
Hammes Mowbray Hall
4'-4" (up to 5'-6") ceiling-to-floor depth made services installation easy but window heights should have been adjusted. 1'-4" for wall thickness too small for all but minimal insulation. More or less linear corridor system, with terminating exit stairs opening directly to outside. Top-down duct distributionfrom attic space - may cause problems of vibration throughout building. Electrical rooms in corner, with adjacent transformer enclosure. Note ventilation louvers in attic. Mail a package. Get arrested. Learn more about building interior.
South wall
44 (avg), 105 (max), Horizontal projection: 164 (avg), 271 (max)
Air / water vapor mixture
A combination of air and gaseous water.
Cooling Degree Days (CDD)
A measure of the need and projected costs of cooling based on a summation of the days that require cooling times the cooling temperature difference.
R value
A measure of the resistance to the flow of heat in h·ft²·ºF/Btu. R = 1/C; R = 1/U
Temperature
Although Celsius °C is the most common temperature measure in the world, Fahrenheit °F is the engineering standard for the US. At -40°, the two scales coincide. The Kelvin scale is used in many scientific calculations. One degree Kelvin (K or °K) equals one degree Celsius °C. The coldest temperature possible is - 273.15°C or 0°K. It is called absolute zero. All objects above absolute zero contain heat. ΔT (delta T) is a commonly used expression for the difference between two temperatures. e.g. ΔT = 212° - 32° = 180°
Human Heat Loss
At the following conditions: air temperature: 23°C, 73°F; skin temperature: 34°C, 93°F Perspiration 17 Watts, Conduction 11 W, Radiation 133 W.The impact of radiant heat loss is underestimated by most people.
Specific Heat
The amount of heat needed to raise the temperature of 1 lb. of a material, 1°F. Specific Heat may be thought of as a dimensionless coefficient of the heat storage potential of a material divided by the heat storage potential of water - Or - In the units: Btu / lb / °F, Also: Btu/ (lb × °F) To find heat amount: E = M × c × ΔT; To find temperature change: ΔT = E ÷ (M × c) Where: E = heat Energy Btu; M = Mass lb; c = specific heat Btu/lb/°F; ΔT = change of Temperature °F. If 1 Btu of energy is added to 1lb of a material, the temperature will rise in inverse proportion to the specific heat.
Latent Heat
The amount of heat resulting from the change of state of all or part of a material.
Specific Heat
The amount of sensible heat that can be stored in a material, per pound, per degree Fahrenheit oftemperature change relative to the specific heat of water. The specific heat of water is 1.0 by definition, Specific heat may also be expressed as 1.0 Btu / lb / ºF.
Thermal Capacitance, Thermal mass
The amount of sensible heat that can be stored in a volume of material per degree Fahrenheit of temperature change. The thermal capacitance is found by multiplying the Specific Heat by the mass of a material. A cubic foot of water has a thermal capacitance of 62.5 Btu / ºF. (1.0 Btu/lb/ºF x 62.5 lbs/ft³)
Sensible Heat
The amount of water vapor in an air / water vapor mixture divided by the maximum amount ofwater vapor possible, for a given temperature and air pressure. (Expressed as a percent)
Massive Construction and Heat
The conduction of heat through a construction assembly is often analyzed separately from the interaction of temperature change and thermal capacitance. General evaluations of the effects of conductivity and thermal mass are simple when the two are separate, but very complex when the effects are analyzed together.
U value
The conduction of heat through an assembly. A measure of the flow of heat in Btu/h·ft²·ºF. U = 1/R
Thermal Stack Effect
The convection caused by temperature differences, and the height difference between the inlet and outlet of the moving air.