1000+ Refrigeration & Air-Conditioning Multiple Choice Question Answer [Solved]

1. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and
A. Carbon dioxide
B. Sulphur dioxide
C. Lithium bromide
D. R-12
Answer : C

2. 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

3. In a vapour compression system, the condition of refrigerant before passing through the condenser is
A. Saturated liquid
B. Wet vapour
C. Dry saturated vapour
D. Superheated vapour
Answer : D

4. The relative coefficient of performance is
A. Actual COP/theoretical COP
B. Theoretical COP/actual COP
C. Actual COP × theoretical COP
D. None of these
Answer : A

5. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The bypass factor of the heating coil is
A. 0.376
B. 0.4
C. 0.6
D. 0.67
Answer : C

6. The lowest thermal diffusivity is of
A. Iron
B. Lead
C. Aluminium
D. Rubber
Answer : D

7. The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called
A. Wet bulb temperature
B. Dry bulb temperature
C. Dew point temperature
D. None of these
Answer : A

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

9. The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
A. Sub-cooling or under-cooling
B. Super-cooling
C. Normal cooling
D. None of these
Answer : A

10. One tonne of refrigeration (1TR) means that the heat removing capacity is
A. 21 kJ/min
B. 210 kJ/min
C. 420 kJ/min
D. 620 kJ/min
Answer : B

11. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
A. Automatic expansion valve
B. High side float valve
C. Thermostatic expansion valve
D. Low side float valve
Answer : D

12. 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

13. The C.O.P. of a refrigerator working on a reversed Carnot cycle is (where T? = Lowest absolute temperature, and T? = Highest absolute temperature)
A. T? / (T? - T?)
B. (T? - T?)/T?
C. (T? - T?)/T?
D. T?/ (T? - T?)
Answer : A

14. The thermostatic expansion valve is also called
A. Constant pressure valve
B. Constant temperature valve
C. Constant superheat valve
D. None of these
Answer : C

15. In aqua ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in
A. Condenser
B. Evaporator
C. Absorber
D. None of these
Answer : A

16. Highest pressure encountered in a refrigeration system should be
A. Critical pressure of refrigerant
B. Much below critical pressure
C. Much above critical pressure
D. Near critical pressure
Answer : B

17. 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

18. 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

19. The wet bulb depression indicates _________ humidity of the air.
A. Absolute
B. Relative
C. Specific
D. None of these
Answer : B

20. The centrifugal compressors are generally used for refrigerants that require
A. Small displacements and low condensing pressures
B. Large displacements and high condensing pressures
C. Small displacements and high condensing pressures
D. Large displacements and low condensing pressures
Answer : D

21. Which of the following cycles uses air as the refrigerant?
A. Ericson
B. Stirling
C. Carnot
D. Bell Coleman
Answer : D

22. A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in ________ power per tonne of refrigeration.
A. Same
B. Lower
C. Higher
D. None of these
Answer : B

23. During a refrigeration cycle, heat is rejected by the refrigerant in a
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : B

24. During sensible heating of air _________ decreases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : B

25. 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

26. The human body feels comfortable when the heat stored in the body is
A. Positive
B. Negative
C. Zero
D. None of these
Answer : C

27. A human body feels comfortable when the heat produced by the metabolism of human body is equal to the
A. Heat dissipated to the surroundings
B. Heat stored in the human body
C. Sum of (A) and (B)
D. Difference of (A) and (B)
Answer : C

28. The coefficient of performance of Electrolux refrigerator is the ratio of
A. Heat supplied by the gas burner to the heat absorbed by the evaporator
B. Heat absorbed by the evaporator to the heat supplied by the gas burner
C. Heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner
D. Heat absorbed by the evaporator minus the heat supplied by the gas burner to the heat absorbed by the evaporator
Answer : B

29. The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is
A. High pressure saturated liquid
B. Wet vapour
C. Very wet vapour
D. Dry vapour
Answer : C

30. 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

31. A one tonne refrigerating machine means that
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
Answer : D

32. In vapour compression cycle the condition off refrigerant is dry saturated vapour
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion or throttle valve
D. Before entering the compressor
Answer : D

33. In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about
A. 1
B. 1.25
C. 2.15
D. 5.12
Answer : B

34. In vapour compression cycle using NH? as refrigerant, initial charge is filled at
A. Suction of compressor
B. Delivery of compressor
C. High pressure side close to receiver
D. Low pressure side near receiver
Answer : C

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

36. Oil separator in a refrigeration cycle is installed
A. Before compressor
B. Between compressor and condenser
C. Between condenser and evaporator
D. Between condenser and expansion valve
Answer : B

37. The mass of water vapour present in __________ is called absolute humidity.
A. 1 m³ of water
B. 1 m³ of dry air
C. 1 kg of wet air
D. 1 kg of dry air
Answer : B

38. In vapour compression cycle, the condition of refrigerant is very wet vapour
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion or throttle valve
D. Before entering the compressor
Answer : D

39. 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

40. 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

41. It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be
A. Dehumidification
B. Cooling and humidification
C. Cooling and dehumidification
D. Dehumidification and pure sensible cooling
Answer : C

42. The reciprocating refrigerant compressors are very suitable for
A. Small displacements and low condensing pressures
B. Large displacements and high condensing pressures
C. Small displacements and high condensing pressures
D. Large displacements and low condensing pressures
Answer : C

43. In vapour compression cycle the condition of refrigerant is superheated vapour
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion or throttle valve
D. Before entering the expansion valve
Answer : B

44. Short horizontal lines on pressure-enthalpy chart show
A. Constant pressure lines
B. Constant temperature lines
C. Constant total heat lines
D. Constant entropy lines
Answer : A

45. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
A. Operating the machine at higher speeds
B. Operating the machine at lower speeds
C. Raising the higher temperature
D. Lowering the higher temperature
Answer : D

46. Critical temperature is the temperature above which
A. A gas will never liquefy
B. A gas will immediately liquefy
C. Water will evaporate
D. Water will never evaporate
Answer : A

47. 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

48. In a psychrometric chart, specific humidity (moisture content) lines are
A. Vertical and uniformly spaced
B. Horizontal and uniformly spaced
C. Horizontal and non-uniformly spaced
D. Curved lines
Answer : B

49. The bank of tubes at the back of domestic refrigerator is
A. Condenser tubes
B. Evaporator tubes
C. Refrigerant cooling tubes
D. Capillary tubes
Answer : A

50. Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of COP of reversed Carnot Cycle?
A. 1.25
B. 0.8
C. 0.5
D. 0.25
Answer : D