# Air-Conditioning Questions and Answers – Psychrometry – Thermodynamic Wet Bulb Temperature

This set of Air-Conditioning Multiple Choice Questions & Answers (MCQs) focuses on “Psychrometry – Thermodynamic Wet Bulb Temperature”.

1. What is the alternate name for thermodynamic wet-bulb temperature?
a) Isobaric WBT
b) Isobaric Saturation Temperature

Explanation: The thermodynamic wet-bulb temperature is also known as adiabatic saturation temperature due to the process involved in it.

2. What is the temperature at which air can be brought to saturation state adiabatically?
a) Thermodynamic WBT
b) Thermodynamic DBT
c) Thermodynamic DPT
d) DPT

Explanation: The temperature at which air can be brought to saturation state adiabatically is called a thermodynamic wet-bulb temperature or adiabatic saturation temperature.

3. Which of the following is carried out to obtain saturation state at the thermodynamic WBT?
a) Condensation
b) Evaporation
c) Compression
d) Expansion

Explanation: The temperature at which air can be brought to saturation state adiabatically is called a thermodynamic wet-bulb temperature or adiabatic saturation temperature. This state is achieved by evaporation of water into the flowing air.

4. Which of the following is the major equipment in the simplest form is used to do saturation of air?
a) Chamber
b) Vessel
c) Insulated Chamber
d) Pipe

Explanation: The equipment used for saturation of the air in the simplest form is an insulated chamber containing an optimum amount of water.

5. The arrangement for extra-water to flow into the chamber from its top is called as ___________
a) chamber ingot
b) chamber gate
c) make-up gate
d) make-up water

Explanation: The equipment used for saturation of the air in the simplest form is an insulated chamber containing an optimum amount of water. In order to get more water into the chamber, an arrangement is provided, which is called make-up water.
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6. What is the ratio of humidity ratio of entering and discharging air?
a) W2 / W1 = (hs2 – hfw) + ha2 – ha1 / (hs1 – hfw)
b) W1 / W2 = (hs1 – hfw) + ha2 – ha1 / (hs2 – hfw)
c) W1 / W2 = (hs2 – hfw) + ha2 – ha1 / (hs1 – hfw)
d) W1 / W2 = (hs2 – hfw) + ha1 – ha2 / (hs1 – hfw)

Explanation: Balancing enthalpies, h1 – W1 hfw = h2 – W2 hfw
As, h1 = ha1 + W1 hs1 and h2 = ha2 + W2 hs2
So, by putting values we get,
W1 / W2 = (hs2 – hfw) + ha2 – ha1 / (hs1 – hfw).

7. The term (h2 – W2 hfw) is known as_________
a) sigma term
b) sigma heat
c) heat factor
d) heat term

Explanation: The term (h2 – W2 hfw) is known as sigma heat, and this term remains constant during the adiabatic process.

8. If h1 = 32 kJ/kg, h2 = 41 kJ/kg, hfw = 49 kJ/kg, W1 = 0.0109 kg/kg of dry air and W2 = 0.0297 kg/kg of dry air then what is the value of sigma heat?
a) 41.0865
b) 39.5447
c) 38.9013
d) 45.8775

Explanation: Sigma heat = (h2 – W2 hfw)
So, putting values in the formula,
Sigma heat = [41 – (49 x 0.0297)] = 39.5447.

9. Evaporation from water to flowing air is carried out adiabatically.
a) False
b) True

Explanation: The temperature at which air can be brought to saturation state adiabatically is called a thermodynamic wet-bulb temperature or adiabatic saturation temperature. This state is achieved by evaporation of water into the flowing air.

10. Make-up water is used to keep the water level constant.
a) True
b) False

Explanation: In order to get more water into the chamber, an arrangement is provided, which is called make-up water. This water is added from the top to keep the water level constant and keep the energy transfer at an optimum pace.

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