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BOMI AHU, Water Treatment, And Plumbing Passed!!
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BOMI AHU, Water Treatment, And Plumbing Passed!!
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BOMI: AHU, Water Treatment, AndPlumbing Passed!!
What is the relationship between thermal comfort and metabolic heat? Answer:
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.
What occupant activity level is chosen when engineers design an air-conditioning
system? Answer: Office 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.
What is the rate of exchange of fresh air for return air based on in an AC system?
Answer: 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.
Define heat Answer: 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.
What happens to the rate of heat transfer if the difference in temperature
increases? Answer: The rate at which heat transfers increases as the
difference in temperature between the two objects increases.
,What are the three methods of heat transfer? Answer: Conduction,
Convection, and Radiation
Define conduction Answer: 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.
Define latent heat Answer: 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.
Define relative humidity Answer: RH (relative humidity) describes the amount
of water vapor held in the air.
Does moist air have more or less density than dry air? Answer: Moist air has
less mass than dry air and is less dense than dry air.
What is the atmospheric pressure of air at sea level? Answer: At sea level,
atmospheric pressure exerts an average force of 14.7 pounds on each square inch
of surface (14.7 psi).
Explain Charles' Law. Answer: 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.
, Explain Boyle's Law. Answer: 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.
How does the human body regulate its temperature? Answer: 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.
What system produces the most heat in a building? Answer: 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.
How have office building AC systems been designed to compensate for heat gain
from office equipment? Answer: To compensate for this heat gain from office
equipment in modern office buildings, air-conditioning systems have been
designed to offset one to three watts per square foot.
What is pull-down load? Answer: Heat left over from the day before must be
removed the following morning when the air-conditioning system is restarted.
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