Refrigeration & Air-Conditioning MCQ Solved Paper for NEET PG

1. The lowest temperature during the cycle in a vapour compression system occurs after
A. Compression
B. Expansion
C. Condensation
D. Evaporation
Answer : D

2. 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

3. The boiling point of ammonia is
A. -10.5°C
B. -30°C
C. -33.3°C
D. -77.7°C
Answer : C

4. Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and ? = Degree of saturation)
A. 0.622 Pv / (Pb - Pv)
B. ?/[1 - (1 - ?) (Ps/Pb)]
C. [Pv (Pb - Pd)]/ [Pd (Pb - Pv)]
D. None of these
Answer : B

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

6. Which of the following is not a desirable property of a refrigerant?
A. High risibility with oil
B. Low boiling point
C. Good electrical conductor
D. Large latent heat
Answer : C

7. 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

8. 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

9. 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

10. A refrigeration system
A. Removes heat from a low temperature body and delivers it to a high temperature body
B. Removes heat from a high temperature body and delivers it to a low temperature body
C. Rejects energy to a low temperature body
D. None of the above
Answer : A

11. 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

12. Carbon dioxide is
A. Colourless
B. Odourless
C. Non-flammable
D. All of these
Answer : D

13. The bypass factor of a cooling coil decreases with
A. Decrease in fin spacing and increase in number of rows
B. Increase in fin spacing and increase in number of rows
C. Increase in fin spacing and decrease in number of rows
D. Decrease in fin spacing and decrease in number of rows
Answer : A

14. In case of sensible cooling of air, the coil efficiency is given by
A. B.P.F. - 1
B. 1 - B.P.F.
C. 1/ B.P.F.
D. 1 + B.P.F.
Answer : B

15. Which of the following refrigerant has the maximum ozone depletion potential in the stratosphere?
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. Fluorine
Answer : D

16. 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

17. 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

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

19. 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

20. In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid
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 : D

21. The superheating in a refrigeration cycle
A. Does not alter C.O.P.
B. Increases C.O.P.
C. Decreases C.O.P.
D. None of these
Answer : C

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

23. Which of the following statement is correct for ammonia as a refrigerant?
A. It is toxic to mucous membranes.
B. It requires large displacement per TR compared to fluoro carbons.
C. It reacts with copper and its alloys.
D. All of these
Answer : D

24. The material of pipe lines for a system using Freon as a refrigerant should be
A. Brass
B. Copper
C. Steel
D. Aluminium
Answer : B

25. The pressure at the inlet of a refrigerant compressor is called
A. Suction pressure
B. Discharge pressure
C. Critical pressure
D. Back pressure
Answer : A

26. Superheating 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 : B

27. An important characteristic of absorption system of refrigeration is
A. Noisy operation
B. Quiet operation
C. Cooling below 0°C
D. Very little power consumption
Answer : B

28. 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

29. If a gas is to be liquefied, its temperature must be
A. Increased to a value above its critical temperature
B. Reduced to a value below its critical temperature
C. Equal to critical temperature
D. None of the above
Answer : C

30. Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since
A. These react with water vapour and cause acid rain
B. These react with plants and cause greenhouse effect
C. These react with oxygen and cause its depletion
D. These react with ozone layer
Answer : D

31. The process, generally used in summer air conditioning to cool and dehumidify the air, is called
A. Humidification
B. Dehumidification
C. Heating and humidification
D. Cooling and dehumidification
Answer : D

32. 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

33. 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

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. In mechanical refrigeration system, the refrigerant has the maximum temperature
A. In evaporator
B. Before expansion valve
C. Between compressor and condenser
D. Between condenser and evaporator
Answer : C

36. The suction pipe diameter of refrigerating unit compressor in comparison to delivery side is
A. Bigger
B. Smaller
C. Equal
D. Smaller/bigger depending on capacity
Answer : A

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

38. The central air conditioning system has ________ overall efficiency as compared to individual systems.
A. Same
B. Lower
C. Higher
D. None of these
Answer : C

39. The process of under-cooling is generally brought about by
A. Circulating more quantity of cooling water through the condenser
B. Using water colder than the main circulating water
C. Employing a heat exchanger
D. Any one of the above
Answer : D

40. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
A. Decreases
B. Increases
C. Remain same
D. Depends on other factors
Answer : B

41. Which of the following refrigerant has the highest freezing point.
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : B

42. A thermostatic expansion valve in a refrigeration system
A. Ensures the evaporator completely filled with refrigerant of the load
B. Is suitable only for constant load systems
C. Maintains different temperatures in evaporator in proportion to load
D. None of the above
Answer : A

43. During heating and humidification, the final relative humidity of air
A. Can be lower or higher than that of the entering air
B. Is lower than that of the entering air
C. Is higher than that of the entering air
D. None of the above
Answer : A

44. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called
A. Dry air
B. Moist air
C. Saturated air
D. Specific humidity
Answer : C

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

46. The relative coefficient of performance is equal to
A. (Theoretical C.O.P.)/ (Actual C.O.P.)
B. (Actual C.O.P.) /(Theoretical C.O.P.)
C. (Actual C.O.P.) × (Theoretical C.O.P.)
D. None of these
Answer : B

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

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

49. For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of
A. Copper
B. Aluminium
C. Steel
D. Brass
Answer : C

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