Heat Transfer, Refrigeration and Air Conditioning problems
- 1. The heat rejection factor (HRF) is given by
Options- A. 1 + C.O.P
- B. 1 - C.O.P.
- C.
- D.
Discuss
Correct Answer:
- 2. 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 Discuss
Correct Answer: 25 mm
- 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 Discuss
Correct Answer: all of the above
- 4. 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 Discuss
Correct Answer: compressor
- 5. The dry bulb temperature during sensible heating of air
Options- A. remains constant
- B. increases
- C. decreases Discuss
Correct Answer: increases
- 6. 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 Discuss
Correct Answer: 2.33
- 7. 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 Discuss
Correct Answer: before entering the compressor
- 8. The vertical and uniformly spaced lines on a psychrometric chart indicates
Options- A. dry bulb temperature
- B. wet bulb temperature
- C. dew point temperature
- D. specific humidity Discuss
Correct Answer: dry bulb temperature
- 9. 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 Discuss
Correct Answer: 0.1 m
- 10. The coefficient of performance of a domestic refrigerator is __________ as compared to a domestic air-conditioner.
Options- A. same
- B. less
- C. more Discuss
Correct Answer: less
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