ASHRAE Psychrometrics and Moist Air Properties

Question 1

What is the dry-bulb temperature of air?

Accepted Answer

Temperature measured by a standard thermometer shielded from radiation and unaffected by moisture evaporation

Answer

Temperature measured by a thermometer wetted with moisture

Answer

Temperature at which air becomes fully saturated with water vapor

Answer

Temperature measured at the dew point condition

Question 2

What does wet-bulb temperature primarily indicate about an air sample?

Accepted Answer

The cooling effect of evaporation, which correlates with the moisture content of the air

Answer

The actual sensible heat content of the air mass

Answer

The dew point temperature of the air

Answer

The temperature achieved only at 100% relative humidity

Question 3

On a standard psychrometric chart, what does the saturation curve (outer boundary) represent?

Accepted Answer

All states where relative humidity equals 100%

Answer

The line of constant enthalpy values

Answer

The boundary between sensible heat and latent heat zones

Answer

The line of constant specific volume

Question 4

How is humidity ratio (W) defined in psychrometrics?

Accepted Answer

Ratio of water vapor mass to dry air mass

Answer

Percentage of water vapor in air by volume

Answer

Ratio of water vapor mass to total moist air mass

Answer

Relative saturation percentage of the air sample

Question 5

What is the dew point temperature of an air sample?

Accepted Answer

The temperature to which air must be cooled at constant pressure for condensation to begin

Answer

The temperature at which ice crystals form within the air mass

Answer

The temperature difference between dry-bulb and wet-bulb readings

Answer

The minimum temperature achievable through adiabatic evaporative cooling

Question 6

In psychrometrics, what does enthalpy (h) represent?

Accepted Answer

Total heat content per unit mass of dry air including both sensible heat and latent heat of water vapor

Answer

Total sensible heat content of dry air only

Answer

Partial pressure exerted by water vapor in the air mixture

Answer

Temperature differential driving heat transfer across HVAC coils

Question 7

What standard atmospheric pressure does ASHRAE use as the baseline for psychrometric calculations?

Accepted Answer

14.696 psia (101.325 kPa)

Answer

14.0 psia (96.5 kPa)

Answer

15.0 psia (103.4 kPa)

Answer

13.5 psia (93.1 kPa)