Discussion
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- Question
The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by
Options- A. (C.O.P.)P = (C.O.P.)R + 2
- B. (C.O.P.)P = (C.O.P.)R + 1
- C. (C.O.P)P = (C.O.P)R - 1
- D. (C.O.P)P = (C.O.P)R
- Correct Answer
- (C.O.P.)P = (C.O.P.)R + 1
- 1. Film coefficient is defined as the ratio of
Options- A. thermal conductivity to the equivalent thickness of the film of fluid
- B. temperature drop through the films of fluids to the thickness of film of fluids
- C. thickness of film of fluid to the thermal conductivity
- D. thickness of film of fluid to the temperature drop through the films of fluids Discuss
- 2. Kirchhoff's law states that
Options- A. the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
- B. the wave length corresponding to the maximum energy is proportional to the absolute temperature
- C. the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
- D. none of the above Discuss
- 3. Which of the following statement is wrong?
Options- A. The value of C.O.P. is always greater than one.
- B. In a vapour compression system, the condition of refrigerant before entering the compressor is dry saturated vapour.
- C. The space between the saturated liquid line and saturated vapour line, in a pressure enthalpy chart, is wet vapour region.
- D. none of the above Discuss
- 4. The heat of sun reaches to us according to
Options- A. conduction
- B. convection
- C. radiation
- D. none of these Discuss
- 5. The average value of thermal conductivity for water at 20° C saturate is about 0.51.
Options- A. True
- B. False Discuss
- 6. In a reversed Brayton cycle, the heat is absorbed by the air during
Options- A. isentropic compression process
- B. constant pressure cooling process
- C. isentropic expansion process
- D. constant pressure expansion process Discuss
- 7. In mechanical refrigeration system, the refrigerant has the maximum temperature
Options- A. in evaporator
- B. before expansion valve
- C. between compressor and condenser
- D. between condenser and evaporator Discuss
- 8. Moisture should be removed from refrigerants to avoid
Options- A. freezing at the expansion valve
- B. restriction to refrigerant flow
- C. corrosion of steel plates
- D. all of these Discuss
- 9. In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is
Options- A. reversed Carnot cycle
- B. reversed Joule cycle
- C. reversed Brayton cycle
- D. reversed Otto cycle Discuss
- 10. The critical thickness of insulation for a sphere is
Options- A. k/h0
- B. 2k/h0
- C. h0/k
- D. h0/2k Discuss
Heat Transfer, Refrigeration and Air Conditioning problems
Search Results
Correct Answer: thermal conductivity to the equivalent thickness of the film of fluid
Correct Answer: the ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
Correct Answer: none of the above
Correct Answer: radiation
Correct Answer: True
Correct Answer: constant pressure expansion process
Correct Answer: between compressor and condenser
Correct Answer: all of these
Correct Answer: reversed Brayton cycle
Correct Answer: 2k/h0
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