Refrigeration & Air-Conditioning MCQ Solved Paper for GMAT

1. The boiling point of carbon dioxide is
A. -20.5°C
B. -50°C
C. -63.3°C
D. -78.3°C
Answer : D

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

3. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then
A. Bigger cabinet should be used
B. Smaller cabinet should be used
C. Perfectly tight vapour seal should be used
D. Refrigerant with lower evaporation temperature should be used
Answer : C

4. The curved lines on a psychrometric chart indicates
A. Dry bulb temperature
B. Wet bulb temperature
C. Dew point temperature
D. Relative humidity
Answer : D

5. One of the purposes of sub cooling the liquid refrigerant is to
A. Reduce compressor overheating
B. Reduce compressor discharge temperature
C. Increase cooling effect
D. Ensure that only liquid and not the vapour enters the expansion (throttling) valve
Answer : D

6. The minimum temperature to which water can be cooled in a cooling tower is
A. Dew point temperature of air
B. Wet bulb temperature of air
C. Dry bulb temperature of air
D. Ambient air temperature
Answer : B

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

8. Domestic refrigerator working on vapour compression cycle uses the following type of expansion device
A. Electrically operated throttling valve
B. Manually operated valve
C. Thermostatic valve
D. Capillary tube
Answer : D

9. The domestic refrigerator uses following type of compressor
A. Centrifugal
B. Axial
C. Miniature sealed unit
D. Piston type reciprocating
Answer : D

10. R-12 is generally preferred over R-22 in deep freezers since
A. It has low operating pressures
B. It gives higher coefficient of performance
C. It is miscible with oil over large range of temperatures
D. All of the above
Answer : C

11. The COP of a domestic refrigerator
A. Is less than 1
B. Is more than 1
C. Is equal to 1
D. Depends upon the make
Answer : B

12. Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.
A. Equalise
B. Reduce
C. Increase
D. None of these
Answer : C

13. The unit of thermal diffusivity is
A. m/hK
B. m/h
C. m²/h
D. m²/hK
Answer : C

14. The C.O.P. of a Carnot refrigerator in winter will be _________ as compared to C.O.P. in summer.
A. Same
B. Lower
C. Higher
D. None of these
Answer : C

15. A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
A. 1 kW
B. 2 kW
C. 3 kW
D. 4 kW
Answer : D

16. The leaks in a refrigeration system using Freon are detected by
A. Halide torch which on detection produces greenish flame lighting
B. Sulphur sticks which on detection gives white smoke
C. Using reagents
D. Smelling
Answer : A

17. Pressure of water vapour is given by
A. 0.622 P_v/ (P_b - P_v)
B. ?/[1 - (1 - ?) (P_s/P_b)]
C. [P_v (P_b - P_d)]/ [P_d (P_b - P_v)]
D. None of these
Answer : D

18. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be
A. 1/4
B. 1/3
C. 3
D. 4
Answer : D

19. Most thermostatic expansion valves are set for a superheat of
A. 5°C
B. 10°C
C. 15°C
D. 20°C
Answer : A

20. The capacity of a domestic refrigerator is in the range of
A. 0.1 to 0.3 TR
B. 1 to 3 TR
C. 3 to 5 TR
D. 5 to 7 TR
Answer : A

21. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by
A. Liquid pump
B. Generator
C. Absorber and generator
D. Absorber, generator and liquid pump
Answer : D

22. As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.
A. Same as
B. Lower than
C. Higher than
D. None of these
Answer : B

23. The general rule for rating refrigeration systems (excepting for CO? system) is to approximate following h.p. per ton of refrigeration
A. 0.1 to 0.5 h.p. per ton of refrigeration
B. 0.5 to 0.8 h.p. per ton of refrigeration
C. 1 to 2 h.p. per ton of refrigeration
D. 2 to 5 h.p. per ton of refrigeration
Answer : C

24. Wet bulb temperature is the temperature of air recorded by a thermometer, when
A. It is not affected by the moisture present in the air
B. Its bulb is surrounded by a wet cloth exposed to the air
C. The moisture present in it begins to condense
D. None of the above
Answer : B

25. For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is ________ that for counter flow.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A

26. 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

27. One ton of the refrigeration is
A. The standard unit used in refrigeration problems
B. The cooling effect produced by melting 1 ton of ice
C. The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours
D. The refrigeration effect to produce 1 ton of ice at NTP conditions
Answer : C

28. In vapour compression cycle, the condition of refrigerant is saturated liquid
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion throttle valve
D. Before entering the expansion valve
Answer : A

29. 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

30. Pick up the wrong statement. A refrigerant should have
A. Tow specific heat of liquid
B. High boiling point
C. High latent heat of vaporisation
D. Higher critical temperature
Answer : B

31. The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will
A. Increase
B. Decrease
C. May increase or decrease depending on the type of refrigerant used
D. Remain unaffected
Answer : A

32. 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

33. 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

34. In a refrigerating machine, heat rejected is _________ heat absorbed.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

35. 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

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

37. The operating temperature of a cold storage is 2°C. The heat leakage from the surrounding is 30 kW for the ambient temperature of 40°C. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is
A. 1.86 kW
B. 3.72 kW
C. 7.44 kW
D. 18.6 kW
Answer : D

38. The boiling point of ammonia is
A. 100°C
B. 50°C
C. 33.3°C
D. 0°C
Answer : C

39. Air conditioning means
A. Cooling
B. Heating
C. Dehumidifying
D. All of these
Answer : D

40. The condition of refrigerant as it leaves the compressor in a vapour compression system is
A. Saturated liquid
B. Wet vapour
C. Dry saturated vapour
D. Superheated vapour
Answer : D

41. Freon group of refrigerants are
A. Inflammable
B. Toxic
C. Non-inflammable and toxic
D. Nontoxic and non-inflammable
Answer : D

42. A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is
A. Ammonia
B. Carbon dioxide
C. Freon
D. Brine
Answer : B

43. The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.
A. More
B. Less
C. Equally
D. Unpredictable
Answer : A

44. The superheated vapour region, in a pressure enthalpy chart, is represented by the space
A. To the left of saturated liquid line
B. To the right of saturated liquid line
C. Between the saturated liquid line and saturated vapour line
D. None of the above
Answer : C

45. An infinite parallel planes with emissivities e? and e?, the interchange factor for radiation from surface 1 to surface 2 is given by
A. (e? + e?)/ e? + e? - e?e?
B. 1/e? + 1/e?
C. e? + e?
D. e?e?
Answer : A

46. Bell Coleman cycle is a
A. Reversed Carnot cycle
B. Reversed Otto cycle
C. Reversed Joule cycle
D. Reversed Rankine cycle
Answer : C

47. 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

48. Chaperon equation is a relation between
A. Temperature, pressure and enthalpy
B. Specific volume and enthalpy
C. Temperature and enthalpy
D. Temperature, pressure, specific volume and enthalpy
Answer : D

49. In a vapour compression refrigeration system, a throttle valve is used in place of an expander because
A. It considerably reduces mass of the system
B. It improves the C.O.P., as the condenser is small
C. The positive work in isentropic expansion of liquid is very small
D. It leads to significant cost reduction
Answer : C

50. In a reversed Brayton cycle, the heat is absorbed by the air during
A. Isentropic compression process
B. Constant pressure cooling process
C. Isentropic expansion process
D. Constant pressure expansion process
Answer : D