Chapter 35 - psychometrics review questions

At standard atmospheric pressure, air has a density of:

0.075 1b/cub.ft

Multiplying the density of a gas and its specific volume together will always produce a result equal to:

1

If the wet-bulb depression is 0°F, what is the relative humidity of the air sample?

100%

If the dry-bulb temperature is 75°F and the wet-bulb temperature is 60°F, the wet-bulb depression is:

15F

If the density of a gas is 0.5 lb/cub.ft, what is its specific volume?

2 cub.ft/lb

What is the dew point temperature of a 75°F air sample with a relative humidity of 60%?

60F

If an air sample holds 60 grains of moisture (per pound) and has the ability to hold a maximum of 90 grains of moisture (per pound), what is the relative humidity of the air sample?

67%

According to the summer comfort chart, Figure 35.6(A), people will generally be comfortable when exposed to which of the following sets of conditions?

75°F @ 50% relative humidity

Air is primarily made up of:

78% nitrogen, 21% oxygen.

Enthalpy is expressed in which of the following units?

BTU/lb

In a cooling-only process, all of the following are true except: a. the dry-bulb temperature drops. b. the wet bulb temperature drops. c. the absolute humidity drops. d. the specific volume of the air drops.

C. the absolute humidity drops.

The body gives off heat in all of the following ways except:

Condensation

In order for an evaporator to remove moisture from the airstream passing through it, the evaporator coil must be at a temperature that is lower than the air's:

Dew point temperature

On the psychrometric chart, the scale along the bottom of the chart represents:

Dry bulb temperature

The term used to describe the random air that leaks into a structure is:

Infiltration

Air that contains all of the moisture that it can hold is referred to as being:

Saturated

Which of the following is true regarding wet-bulb and dry-bulb temperatures?

The wet-bulb temperature reading can be equal to the dry-bulb temperature reading.

If only the absolute humidity of an air sample is known, which of the following values can be determined from the psychrometric chart?

Wet bulb temperatures

The term enthalpy applies to:

a combination of latent heat and sensible heat.

Which of the following is a correct formula for total heat? a. QT = QS ÷ QL b. QT = QS+ QL c. QT = QS × QL d. OT = QS - QL

b. QT = QS+ QL

According to the winter comfort chart, Figure 35.6(B), people will generally be comfortable when exposed to which of the following sets of conditions?

70°F @ 50% relative humidity

Of the following sets of air properties, which two can be identified by following the same line?

Enthalpy and wet-bulb temperature

Relative humidity is measured using what instrument?

Psychrometer

The nitrogen and oxygen in our air are classified as a. subcooled gases. b. inert gases. c. superheated gases. d. saturated gases.

c. superheated gases.

Condensate dripping from an air-conditioning system is an indication that the evaporator coil temperature is:

cooler than the air's dew point temperature.

Which of the following statements is true regarding the heating of an air sample? a. The dry-bulb temperature will drop and the wet-bulb temperature will rise. b. The relative humidity will rise and the absolute humidity will remain the same. c. The dry-bulb temperature will rise and the wet bulb temperature will drop. d. The relative humidity will drop and the absolute humidity will remain the same.

d. The relative humidity will drop and the absolute humidity will remain the same.