# Psychrometrics - Mechanical Engineering (MCQ) questions and answers

1)   What is the perfect condition for dehumidification of air?

a. air is heated above its dew point temperature
b. air is cooled up to its dew point temperature
c. air is heated below its dew point temperature
d. air is cooled below its dew point temperature
 Answer  Explanation ANSWER: air is cooled below its dew point temperature Explanation: No explanation is available for this question!

2)   When the rate of evaporation of water is zero, the relative humidity of the air is

a. 0%
b. 100%
c. 50%
d. unpredictable
 Answer  Explanation ANSWER: 100% Explanation: No explanation is available for this question!

3)   When,
H1 = Total heat of air entering the coil (heating or cooling)
H2 = Total heat of air leaving the coil (heating or cooling)
H3 = Total heat of air at the end of the process (humidification or dehumidification)
then, the sensible heat factor (H2 – H1) / (H3 – H1) represents the process of

a. cooling and humidification
b. cooling and dehumidification
c. heating and humidification
d. heating and dehumidification
 Answer  Explanation ANSWER: heating and humidification Explanation: No explanation is available for this question!

4)   The dew point temperature is less than the wet bulb temperature for

a. saturated air
b. unsaturated air
c. both saturated and unsaturated air
d. none of the above
 Answer  Explanation ANSWER: unsaturated air Explanation: No explanation is available for this question!

5)   At 100% relative humidity, the wet bulb temperature is

a. lower than the dew point temperature
b. higher than the dew point temperature
c. equal to the dew point temperature
d. none of the above
 Answer  Explanation ANSWER: equal to the dew point temperature Explanation: No explanation is available for this question!

6)   Humidification is the process of addition moisture in air at

a. constant wet bulb temperature
b. constant dry bulb temperature
c. constant latent heatn
d. none of the above
 Answer  Explanation ANSWER: constant dry bulb temperature Explanation: No explanation is available for this question!

7)   Air at dry bulb temperature Td1 is passed through the heating coil and some amount of air is by passed unaffected and leaves with dry bulb temperature Tb2 and the temperature of heated air is Td3 (where Td2 < Td3), what is the correct formula for by pass factor (The amount of air by passed unaffected)?

a. Bypass Factor = (Td3 – Td2) / (Td3 – Td1)
b. Bypass Factor = (Td3 – Td1) / (Td3 – Td2)
c. Bypass Factor = (Td2 – Td1) / (Td2 – Td3)
d. Bypass Factor = (Td2 – Td3) / (Td2 – Td1)
 Answer  Explanation ANSWER: Bypass Factor = (Td2 – Td3) / (Td2 – Td1) Explanation: No explanation is available for this question!

8)   The horizontal line in psychrometric chart joining the change of state of air represents

a. humidification
b. sensible cooling or heating
c. sensible cooling or heating with humidification
d. sensible cooling or heating with dehumidification
 Answer  Explanation ANSWER: sensible cooling or heating Explanation: No explanation is available for this question!

9)   The moisture content lines in psychrometric chart are also called as

a. relative humidity lines
b. specific humidity lines
c. both a. and b.
d. none of the above
 Answer  Explanation ANSWER: specific humidity lines Explanation: No explanation is available for this question!

10)   At any point on the saturation curve in psychometric chart, the dry bulb temperature is always

a. less than the corresponding wet bulb temperature
b. more than the corresponding wet bulb temperature
c. equal to the corresponding wet bulb temperature
d. cannot predict
 Answer  Explanation ANSWER: equal to the corresponding wet bulb temperature Explanation: No explanation is available for this question!

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