BOMI: AHU, Water Treatment, and Plumbing
1. What is the relationship between thermal comfort and metabolic heat?: Thermal
comfort exists when the temperature and relative humidity of a person's environment permit the person to lose, without
conscious effort, metabolic heat at the same rate he or she produces it. Because temperature and humidity combine
to make
humans feel comfortable in their surroundings, these characteristics must be adjusted by the AC system in order to
enhance human comfort.
2. What occupant activity level is chosen when engineers design an air-con-
ditioning system?: Oflce building air-conditioning systems are typically designed to accommodate people
engaged in sedentary activities, including tasks done while seated or standing. Sedentary activity is the most important
condition because when people are sedentary, they think about their comfort or discomfort.
3. What is the rate of exchange of fresh air for return air based on in an AC
system?: The rate of exchange of fresh air for returned air is based on the quantity of fresh air required for each
building occupant over the course of time.
4. Define heat: Heat is energy that flows from one object to another. Heat always travels from an object with more
heat to an object with less heat until both bodies are the same temperature.
,5. What happens to the rate of heat transfer if the difference in temperature
increases?: The rate at which heat transfers increases as the difference in temperature between the two objects
increases.
6. What are the three methods of heat transfer?: Conduction, Convection, and Radiation
7. Define conduction: Conduction is the direct transfer of heat from one body to another. The substances have
to be in physical contact with each other, but there is no movement of the material itself.
8. Define latent heat: Latent heat is the energy that is used or released during a change of state. Latent heat
cannot be felt or measured with a thermometer because it is hidden within a substance.
9. Define relative humidity: RH (relative humidity) describes the amount of water vapor held in the air.
10. Does moist air have more or less density than dry air?: Moist air has less mass than dry
air and is less dense than dry air.
11. What is the atmospheric pressure of air at sea level?: At sea level, atmospheric pressure
exerts an average force of 14.7 pounds on each square inch of surface (14.7 psi).
,12. Explain Charles' Law.: Charles' law explains why gases expand when heated and contract when cooled.
Given a certain quantity of gas, as temperature increases, volume increases. This is because the molecules have the
opportunity to move more and spread out. As pressure increases and the volume decreases, the temperature will
, increase because compressing the gas causes the molecules to
vibrate faster and collide into each other more frequently, causing friction heat.
13. Explain Boyle's Law.: Boyle's law states that at a constant temperature, as the volume increases, the
pressure decreases. If the pressure on a
certain amount of gas is doubled, the volume of space it requires will be cut in half. As pressure goes up, volume goes
down.
14. How does the human body regulate its temperature?: The body dissipates heat by
sending blood from internal organs to the skin where the heat is thrown off into the
surroundings by radiant heat loss, convective heat loss, or evaporation. Perspiring and losing the heat through
evaporation is an evaporative cooling process and is used in air-conditioning systems as well as human bodies.
15. What system produces the most heat in a building?: Building lights are the most
significant internal heat source. The heat given off by lights depends mainly on the wattage rating of the lighting
elements. Lighting systems produce heat loads of up to four watts per square foot. The heat gain from one watt of
electrical energy is equivalent to 3.4 Btu per hour.
16. How have office building AC systems been designed to compensate for heat
gain from office equipment?: To compensate for this heat gain from oflce equipment in modern oflce
buildings, air-conditioning systems have been designed to offset one to three watts per square foot.
1. What is the relationship between thermal comfort and metabolic heat?: Thermal
comfort exists when the temperature and relative humidity of a person's environment permit the person to lose, without
conscious effort, metabolic heat at the same rate he or she produces it. Because temperature and humidity combine
to make
humans feel comfortable in their surroundings, these characteristics must be adjusted by the AC system in order to
enhance human comfort.
2. What occupant activity level is chosen when engineers design an air-con-
ditioning system?: Oflce building air-conditioning systems are typically designed to accommodate people
engaged in sedentary activities, including tasks done while seated or standing. Sedentary activity is the most important
condition because when people are sedentary, they think about their comfort or discomfort.
3. What is the rate of exchange of fresh air for return air based on in an AC
system?: The rate of exchange of fresh air for returned air is based on the quantity of fresh air required for each
building occupant over the course of time.
4. Define heat: Heat is energy that flows from one object to another. Heat always travels from an object with more
heat to an object with less heat until both bodies are the same temperature.
,5. What happens to the rate of heat transfer if the difference in temperature
increases?: The rate at which heat transfers increases as the difference in temperature between the two objects
increases.
6. What are the three methods of heat transfer?: Conduction, Convection, and Radiation
7. Define conduction: Conduction is the direct transfer of heat from one body to another. The substances have
to be in physical contact with each other, but there is no movement of the material itself.
8. Define latent heat: Latent heat is the energy that is used or released during a change of state. Latent heat
cannot be felt or measured with a thermometer because it is hidden within a substance.
9. Define relative humidity: RH (relative humidity) describes the amount of water vapor held in the air.
10. Does moist air have more or less density than dry air?: Moist air has less mass than dry
air and is less dense than dry air.
11. What is the atmospheric pressure of air at sea level?: At sea level, atmospheric pressure
exerts an average force of 14.7 pounds on each square inch of surface (14.7 psi).
,12. Explain Charles' Law.: Charles' law explains why gases expand when heated and contract when cooled.
Given a certain quantity of gas, as temperature increases, volume increases. This is because the molecules have the
opportunity to move more and spread out. As pressure increases and the volume decreases, the temperature will
, increase because compressing the gas causes the molecules to
vibrate faster and collide into each other more frequently, causing friction heat.
13. Explain Boyle's Law.: Boyle's law states that at a constant temperature, as the volume increases, the
pressure decreases. If the pressure on a
certain amount of gas is doubled, the volume of space it requires will be cut in half. As pressure goes up, volume goes
down.
14. How does the human body regulate its temperature?: The body dissipates heat by
sending blood from internal organs to the skin where the heat is thrown off into the
surroundings by radiant heat loss, convective heat loss, or evaporation. Perspiring and losing the heat through
evaporation is an evaporative cooling process and is used in air-conditioning systems as well as human bodies.
15. What system produces the most heat in a building?: Building lights are the most
significant internal heat source. The heat given off by lights depends mainly on the wattage rating of the lighting
elements. Lighting systems produce heat loads of up to four watts per square foot. The heat gain from one watt of
electrical energy is equivalent to 3.4 Btu per hour.
16. How have office building AC systems been designed to compensate for heat
gain from office equipment?: To compensate for this heat gain from oflce equipment in modern oflce
buildings, air-conditioning systems have been designed to offset one to three watts per square foot.
