Heat Transfer, Refrigeration and Air Conditioning problems
- 1. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
Options- A. operating the machine at higher speeds
- B. operating the machine at lower speeds
- C. raising the higher temperature
- D. lowering the higher temperature Discuss
Correct Answer: lowering the higher temperature
- 2. A one tonne refrigerating machine means that
Options- A. one tonne is the total mass of machine
- B. one tonne refrigerant is used
- C. one tonne of water can be converted into ice
- D. one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min Discuss
Correct Answer: one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
- 3. The cooling of air, without any change in its specific humidity, is known as sensible cooling.
Options- A. Correct
- B. Incorrect Discuss
Correct Answer: Correct
- 4. The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called
Options- A. humidity ratio
- B. relative humidity
- C. absolute humidity
- D. degree of saturation Discuss
Correct Answer: degree of saturation
- 5. The air cooling system mostly used in transport type aircrafts is
Options- A. simple air cooling system
- B. simple evaporative air cooling system
- C. boot-strap air cooling system
- D. all of these Discuss
Correct Answer: boot-strap air cooling system
- 6. The evaporator used in house-hold refrigerators is
Options- A. frosting evaporator
- B. non-frosting evaporator
- C. defrosting evaporator
- D. none of these Discuss
Correct Answer: frosting evaporator
- 7. The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.
Options- A. increases
- B. decreases Discuss
Correct Answer: increases
- 8. Dehydration is the process of removing water vapour from the surrounding air.
Options- A. True
- B. False Discuss
Correct Answer: True
- 9. If the evaporator temperature is kept constant, the coefficient of performance of a refrigeration cycle __________ with the increase in condenser temperature.
Options- A. increases
- B. decreases Discuss
Correct Answer: decreases
- 10. The heat transfer by conduction through a thick cylinder(Q) is given by (where T1 = Higher temperature, T2 = Lower temperature, r1 = Inside radius, r2 = Outside radius, l = Length of cylinder, and k = Thermal conductivity)
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
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