ASHRAE Psychrometrics and Moist Air Properties 1

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

Dry-bulb temperature is the temperature of air measured by a standard thermometer shielded from radiation and not influenced by moisture content or evaporation.

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

Wet-bulb temperature measures the cooling effect of water evaporating from a wetted thermometer wick, providing an indirect measure of the air's moisture content.

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 saturation curve is the locus of all air states at 100% relative humidity, representing fully saturated air at each dry-bulb temperature.

Question 4

How is humidity ratio (W) defined in psychrometrics?

Accepted Answer

Ratio of water vapor mass to dry air mass

Answer

Humidity ratio W is defined as the mass of water vapor per unit mass of dry air (lb_w/lb_da or kg_w/kg_da), and remains constant during sensible heating or cooling.

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

Dew point is the temperature at which air, cooled at constant pressure and constant humidity ratio, reaches saturation and water vapor begins to condense.

ASHRAE - American Society of Heating, Refrigeration and Air Conditioning Engineers Certification Practice Test

ASHRAE - American Society of Heating, Refrigeration and Air Conditioning Engineers Certification Practice Test

ASHRAE Psychrometrics and Moist Air Properties 1