Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning

31. 

A composite slab has two layers of different materials with thermal conductivities k1 and k2. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be

A. k1 k2
B. k1 + k2
C.
D.

Answer: Option D

Explanation:

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32. 

The critical temperature is the temperature

A. below which a gas does not obey gas laws
B. above which a gas may explode
C. below which a gas is always liquified
D. above which a gas will never liquified

Answer: Option D

Explanation:

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33. 

The evaporator changes the low pressure liquid refrigerant from the expansion valve into

A. high pressure liquid refrigerant
B. low pressure liquid and vapour refrigerant
C. low pressure vapour refrigerant
D. none of these

Answer: Option C

Explanation:

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34. 

For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is

A. zero
B. 20
C. 50
D. 100

Answer: Option D

Explanation:

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35. 

In case ofsensible cooling of air, the coil efficiency is given by

A. B.P.F. - 1
B. 1 - B.P.F.
C.
D. 1 + B.P.F.

Answer: Option B

Explanation:

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