Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning

36. 

A furnace is made of a red brick wall of thickness 0.5 m and conductivity 0.7 W/mK. For the same heat loss and temperature drop, this can be replaced by a layer of diatomite earth of conductivity 0.14 W/mK and thickness

A. 0.5 m
B. 0.1 m
C. 0.2 m
D. 0.5 m

Answer: Option B

Explanation:

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37. 

In a refrigeration system, the expansion device is connected between the

A. compressor and condenser
B. condenser and receiver
C. receiver and evaporator
D. evaporator and compressor

Answer: Option C

Explanation:

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38. 

The heat rejection factor (HRF) is given by

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

Answer: Option C

Explanation:

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39. 

Wein's law states that the wave length corresponding to __________ is proportional to the absolute temperature.

A. minimum energy
B. maximum energy

Answer: Option B

Explanation:

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40. 

In a domestic vapour compression refrigerator, the refrigerant commonly used is

A. CO2
B. Ammonia
C. R-12
D. all of these

Answer: Option C

Explanation:

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