A reversible engine has ideal thermal efficiency of 30%. When it is used as a re

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Question
A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be
Options
A. 1.33
B. 2.33
C. 3.33
D. 4.33

Correct Answer

2.33

Heat Transfer, Refrigeration and Air Conditioning problems

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2. In order to collect liquid refrigerant and to prevent it from going to a __________ , a device known as accumulator is used at the suction of compressor.
Options
A. compressor
B. condenser
C. expansion valve
D. evaporator

3. The amount of heat flow through a body by conduction is
Options
A. directly proportional to the surface area of the body
B. directly proportional to the temperature difference on the two faces of the body
C. inversely proportional to the thickness of the body
D. all of the above

4. An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be
Options
A. 25 mm
B. 40 mm
C. 160 mm
D. 800 mm

6. In a vapour compression system, the condition of refrigerant is dry saturated vapour
Options
A. before entering the compressor
B. after leaving the compressor
C. before entering the condenser
D. after leaving the condenser

8. 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
Options
A. 0.5 m
B. 0.1 m
C. 0.2 m
D. 0.5 m

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