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This mock test of Test: Properties of Moist Air - 3 for Mechanical Engineering helps you for every Mechanical Engineering entrance exam.
This contains 10 Multiple Choice Questions for Mechanical Engineering Test: Properties of Moist Air - 3 (mcq) to study with solutions a complete question bank.
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QUESTION: 1

If the measured wet-bulb temperature and the thermodynamic wet-bulb temperature are equal, then the non-dimensional number with a value of unity is the

Solution:

QUESTION: 2

For completely dry air total heat is

Solution:

For completely dry air, since latent part will not be present hence total heat will be equal to total sensible heat.

QUESTION: 3

If two streams of air containing m_{1 }and m_{2} mass of dry air and enthalpy h_{1} and h_{2} are mixed adiabaticaily then

Solution:

For adiabatic mixing

QUESTION: 4

The barometer pressure is 1.03 bar, the partial pressure of air is 1 bar and the saturation partial pressure of water vapour at the same dry bulb temperature is 0.05 bar. What is the relative humidity?

Solution:

Barometer pressure, P = 1.03 bar

P_{vs} = 0.05 bar; P_{a} = 1 bar

QUESTION: 5

Air at state 1 (DPT = 10°C, w = 0.0040 kg/kg) mixes with air at state 2 (DPT = 18°C, w = 0.0051 kg/kg) in the ratio 1 to 3 by weight. The degree of saturation (%) of the mixture is (The specific humidity of saturated air at 13.6°C. w = 0.01 kg/kg)

Solution:

kg of moisture actually contained

kg of moisture in saturated air of mixture

= 0.01 kg/kg of air

Degree of saturation

QUESTION: 6

For air with a relative humidity of 80%

Solution:

For unsaturated air

DBT > WBT > DPT

QUESTION: 7

For a typical sample of ambient air (at 30°C, 75% relative humidity and standard atmospheric pressure), the amount of moisture in kg per kg of dry air will be approximately

Solution:

QUESTION: 8

5 gm of water vapour per kg of air is removed and temperature of air after removing water vapour is 25°C DBT.

Find the relative humidity. Use following table,

Solution:

w_{1} = 0.0218 kg vapour/kg of dry air

After removing 5 gm

w_{2} = 0.0168

QUESTION: 9

Air at state 1 (DPT = 1°C, w= 0.0040 kg/kg of da) mixes with air at state 2 (DPT = 18°C, w = 0.0051 kg/kg of da) in the ratio of 1 to 3 by weight the degree of saturation (%) of the mixture is (The specific humidity of saturated air at 13.6°C, w = 0.01 kg/kg of da)

Solution:

Moisture content in the mixture

kg of moisture in saturated air of mixture

= 0.01 kg/kg of air

Degree of saturation =

QUESTION: 10

A room 7m x 4m x 4m is occupied by an air- water vapour mixture at 38°C. The atmospheric pressure is 1 bar & relative humidity is 70%. The mass of air is (take P_{s} at 38°C = 0.06624 bar)

Solution:

### Properties of Moist Air

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