313D Psychrometrics and Humidity Control

Question 1

What does the term 'psychrometrics' refer to in HVAC?

Accepted Answer

The study of thermodynamic properties of moist air

Answer

The study of chemical reactions in refrigerants

Answer

The measurement of refrigerant pressures in a system

Answer

The analysis of duct static pressure losses

Question 2

What is the dew point temperature?

Accepted Answer

The temperature to which air must be cooled for water vapor to begin condensing

Answer

The temperature at which air reaches maximum velocity through a duct

Answer

The temperature differential across the evaporator coil at design conditions

Answer

The lowest allowable refrigerant suction temperature in the system

Question 3

On a psychrometric chart, wet-bulb temperature lines run in which direction?

Accepted Answer

Diagonally downward from the saturation curve toward the lower right

Answer

Horizontally across the chart

Answer

Vertically parallel to the dry-bulb temperature axis

Answer

In concentric arcs around the origin point

Question 4

What is relative humidity (RH)?

Accepted Answer

The ratio of actual moisture content to the maximum moisture air can hold at that temperature

Answer

The actual mass of water vapor in air measured in grains per pound of dry air

Answer

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

Answer

The temperature at which condensation forms on interior surfaces

Question 5

What is the key difference between sensible heat and latent heat in air conditioning?

Accepted Answer

Sensible heat causes a measurable temperature change; latent heat involves phase change without temperature change

Answer

Sensible heat is removed at the condenser; latent heat is added at the compressor

Answer

Sensible heat relates to refrigerant flow; latent heat relates to air velocity

Answer

There is no practical difference — both describe the same heat transfer mechanism

Question 6

What does enthalpy measure in an HVAC psychrometric context?

Accepted Answer

The total heat content of moist air, combining both sensible and latent heat

Answer

The velocity of conditioned air through supply ductwork

Answer

The pressure differential across the air filter at design airflow

Answer

The static regain in a supply air duct system

Question 7

What indoor relative humidity range does ASHRAE recommend for occupant comfort in residential buildings?

Accepted Answer

30–60%

Answer

10–20%

Answer

70–80%

Answer

85–95%