Refrigeration & Air-Conditioning 1000+ MCQ with answer for SSC Stenographer

1. The coefficient of performance is the ratio of the refrigerant effect to the
A. Heat of compression
B. Work done by compressor
C. Enthalpy increase in compressor
D. All of the above
Answer : D

2. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called
A. Wet bulb temperature
B. Dry bulb temperature
C. Dew point temperature
D. None of these
Answer : B

3. Vertical lines on pressure-enthalpy chart show constant
A. Pressure lines
B. Temperature lines
C. Total heat lines
D. Entropy lines
Answer : C

4. The coefficient of performance of Heat Pump is always __________ one.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

5. Which of the following refrigerants has lowest freezing point?
A. Freon-12
B. NH3
C. CO2
D. Freon-22
Answer : D

6. The higher temperature in vapour compression cycle occurs at
A. Receiver
B. Expansion valve
C. Evaporator
D. Compressor discharge
Answer : D

7. Which of the following statement is wrong?
A. The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.
B. In vapour compression cycle, the useful part of the heat transfer is at the condenser.
C. In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.
D. The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.
Answer : D

8. In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature
A. Which lies between the dry bulb and wet bulb temperatures of the incoming stream
B. Which lies between the wet bulb and dew point temperatures of the incoming stream
C. Which is lower than the dew point temperature of the incoming stream
D. Of adiabatic saturation of incoming stream
Answer : C

9. The colour of the flame of halide torch, in case of leakage of Freon refrigerant, will change to
A. Bright green
B. Yellow
C. Red
D. Orange
Answer : A

10. During sensible cooling,
A. Relative humidity remains constant
B. Wet bulb temperature increases
C. Specific humidity increases
D. Partial pressure of vapour remains constant
Answer : D

11. A refrigerant compressor is used to
A. Raise the pressure of the refrigerant
B. Raise the temperature of the refrigerant
C. Circulate the refrigerant through the refrigerating system
D. All of the above
Answer : D

12. Nusselt number (N_N) is given by
A. N_N = hl/k
B. N_N = ? c_p/k
C. N_N = ? V l /?
D. N_N = V²/t.c_p
Answer : A

13. In Electrolux refrigerator
A. Ammonia is absorbed in hydrogen
B. Ammonia is absorbed in water
C. Ammonia evaporates in hydrogen
D. Hydrogen evaporates in ammonia
Answer : C

14. The vertical and uniformly spaced lines on a psychrometric chart indicates
A. Dry bulb temperature
B. Wet bulb temperature
C. Dew point temperature
D. Specific humidity
Answer : A

15. In aqua ammonia and Lithium bromide water absorption refrigeration systems, the refrigerants are respectively
A. Water and water
B. Water and lithium bromide
C. Ammonia and lithium bromide
D. Ammonia and water
Answer : D

16. Which of the following refrigerant is highly toxic and flammable?
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : A

17. The C.O.P. of an absorption type refrigerator is given by (where T? = Temperature at which the working substance receives heat, T? = Temperature of cooling water, and T? = Evaporator temperature)
A. [T? (T? - T?)] / [T? (T? - T?)]
B. [T? (T? - T?)]/ [T? (T? - T?)]
C. [T? (T? - T?)] / [T? (T? - T?)]
D. [T? (T? - T?)] / [T? (T? - T?)]
Answer : B

18. Most of the domestic refrigerators work on the following refrigeration system
A. Vapour compression
B. Vapour absorption
C. Carnot cycle
D. Electrolux refrigerator
Answer : A

19. The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner.
A. Same
B. Less
C. More
D. None of these
Answer : B

20. Absorption system normally uses the following refrigerant
A. Freon-11
B. Freon-22
C. CO2
D. Ammonia
Answer : D

21. Presence of moisture in a refrigerant affects the working of
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : D

22. The power per tonne of refrigeration is
A. 3.5/C.O.P.
B. C.O.P/3.5
C. 3.5 × C.O.P.
D. None of these
Answer : A

23. In aircraft, air refrigeration Cycle is used because of
A. Low weight per tonne of refrigeration
B. High heat transfer rate
C. Low temperature at high altitudes
D. Higher coefficient of performance
Answer : A

24. A standard ice point temperature corresponds to the temperature of
A. Water at 0°C
B. Ice at 4°C
C. Solid and dry ice
D. Mixture of ice and water under equilibrium conditions
Answer : D

25. The dehumidification process, on the psychrometric chart, is shown by
A. Horizontal line
B. Vertical line
C. Inclined line
D. Curved line
Answer : B

26. Reducing suction pressure in refrigeration cycle
A. Lowers evaporation temperature
B. Increases power required per ton of refrigeration
C. Lowers compressor capacity because vapour is lighter
D. All of the above
Answer : D

27. The capillary tube, as an expansion device, is used in
A. Domestic refrigerators
B. Water coolers
C. Room air conditioners
D. All of these
Answer : D

28. A vapour absorption refrigeration system
A. Gives noisy operation
B. Gives quiet operation
C. Requires little power consumption
D. Cools below 0°C
Answer : B

29. One ton refrigeration corresponds to
A. 50 kcal/ min
B. 50 kcal/ hr
C. 80 kcal/ min
D. 80 kcal/ hr
Answer : A

30. The specific humidity during heating and humidification process.
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : B

31. In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is
A. Less than 2 kg
B. More than or equal to 3.65 kg
C. More than 10 kg
D. There is no such consideration
Answer : B

32. In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is
A. Reversed Carnot cycle
B. Reversed Joule cycle
C. Reversed Brayton cycle
D. Reversed Otto cycle
Answer : C

33. The evaporator changes the low pressure liquid refrigerant from the expansion valve into
A. High pressure liquid refrigerant
B. Low pressure liquid and vapour refrigerant
C. Low pressure vapour refrigerant
D. None of these
Answer : C

34. 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.
A. Compressor
B. Condenser
C. Expansion valve
D. Evaporator
Answer : A

35. During adiabatic saturation process on unsaturated air __________ remains constant.
A. Relative humidity
B. Dew point temperature
C. Dry bulb temperature
D. Wet bulb temperature
Answer : D

36. The bypass factor for a cooling coil
A. Increases with increase in velocity of air passing through it
B. Decreases with increase in velocity of air passing through it
C. Remains unchanged with increase in velocity of air passing through it
D. May increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering
Answer : A

37. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called
A. Humidity ratio
B. Relative humidity
C. Absolute humidity
D. Degree of saturation
Answer : B

38. For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
A. Small
B. High
C. Equal
D. Anything
Answer : A

39. Ammonia is
A. Non-toxic
B. Non-inflammable
C. Toxic and non-inflammable
D. Highly toxic and inflammable
Answer : D

40. The fluids used in Electrolux refrigerator are
A. Water and hydrogen
B. Ammonia and hydrogen
C. Ammonia, water and hydrogen
D. None of these
Answer : C

41. Under cooling in a refrigeration cycle
A. Increases C.O.P
B. Decreases C.O.P
C. C.O.P remains unaltered
D. Other factors decide C.O.P
Answer : A

42. Rick up the incorrect statement
A. Lithium bromide used in vapour absorption cycle is non volatile
B. Lithium bromide plant can't operate below 0°C
C. A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
D. Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator
Answer : C

43. Condensing temperature in a refrigerator is the temperature
A. Of cooling medium
B. Of freezing zone
C. Of evaporator
D. At which refrigerant gas becomes liquid
Answer : D

44. During heating and dehumidification process, dry bulb temperature
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : B

45. In S.J. unit, one ton of refrigeration is equal to
A. 210 kJ/ min
B. 21 kJ/ min
C. 420 kJ/ min
D. 840 kJ/ min
Answer : A

46. The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for condensing temperatures without non-condensable gases,
A. Will be higher
B. Will be lower
C. Will remain unaffected
D. May be higher or lower depending upon the nature of noncondensable gases
Answer : A

47. The C.O.P. of a heat pump working on a reversed Carnot cycle is
A. T?/(T? - T?)
B. (T? - T?)/T?
C. (T? - T?)/T?
D. T?/(T? - T?)
Answer : D

48. The thermal diffusivity for gases is generally __________ those for liquids.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

49. Formation of frost on evaporator in refrigerator
A. Results in loss of heat due to poor heat transfer
B. Increases heat transfer rate
C. Is immaterial
D. Can be avoided by proper design
Answer : A

50. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
A. Heated and dehumidified
B. Heated and humidified
C. Cooled and humidified
D. Cooled and dehumidified
Answer : B