MCQ on Refrigerator & AC 1-50

1. Freon group of refrigerants are
(A) Inflammable
(B) Toxic
(C) Non-inflammable and toxic
(D) Nontoxic and non-inflammable✔

2. The boiling point of ammonia is
(A) -10.5°C
(B) -30°C
(C) -33.3°C✔
(D) -77.7°C

3. For obtaining high COP, the pressure range of compressor should be
(A) High
(B) Low✔
(C) Optimum
(D) Any value

4. A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be
(A) 1.33
(B) 2.33✔
(C) 3.33
(D) 4.33

5. Cooling water is required for following equipment in ammonia absorption plant
(A) Condenser
(B) Evaporator
(C) Absorber
(D) Condenser, absorber and separator (rectifier)✔

6. The freezing point of sulphur dioxide is
(A) -56.6°C
(B) -75.2°C✔
(C) -77.7°C
(D) -135.8°C

7. Mass flow ratio of NH₃ in comparison to Freon-12 for same refrigeration load and same temperature limits is of the order of
(A) 1: 1
(B) 1: 9✔
(C) 9: 1
(D) 1: 3

8. In a refrigeration system, the expansion device is connected between the
(A) Compressor and condenser
(B) Condenser and receiver
(C) Receiver and evaporator✔
(D) Evaporator and compressor

9. The vapour compression refrigerator employs the following cycle
(A) Rankine
(B) Carnot
(C) Reversed Rankine
(D) Reversed Carnot✔

10. 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

11. Rating of a domestic refrigerator is of the order of
(A) 0.1 ton✔
(B) 5 tons
(C) 10 tons
(D) 40 tons

12. 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)

13. The bank of tubes at the back of domestic refrigerator is
(A) Condenser tubes✔
(B) Evaporator tubes
(C) Refrigerant cooling tubes
(D) Capillary tubes

14. In a lithium bromide absorption refrigeration system
(A) Lithium bromide is used as a refrigerant and water as an absorbent
(B) Water is used as a refrigerant and lithium bromide as an absorbent✔
(C) Ammonia is used as a refrigerant and lithium bromide as an absorbent
(D) None of the above

15. The condition of refrigerant after passing through the condenser in a vapour compression system is
(A) Saturated liquid✔
(B) Wet vapour
(C) Dry saturated vapour
(D) Superheated vapour

16. In a refrigeration cycle, the flow of refrigerant is controlled by
(A) Compressor
(B) Condenser
(C) Evaporator
(D) Expansion valve✔

17. 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

18. For air conditioning the operation theater in a hospital, the percentage of outside air in the air supplied is
(A) Zero
(B) 20
(C) 50
(D) 100✔

19. In vapour compression cycle using NH₃ 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

20. 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

21. Absorption system normally uses the following refrigerant
(A) Freon-11
(B) Freon-22
(C) CO2
(D) Ammonia✔

22. Which of the following statement is correct?
(A) In vapour absorption refrigerator, the compression of refrigerant is avoided.
(B) Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.
(C) In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.
(D) All of the above✔

23. Allowable pressure on high pressure side or ammonia absorption system is of the order of
(A) Atmospheric pressure
(B) Slightly above atmospheric pressure
(C) 24 bars
(D) 56 bars✔

24. 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

25. 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✔

26. During humidification process, __________ increases.
(A) Wet bulb temperature
(B) Relative humidity✔
(C) Dry bulb temperature
(D) Specific humidity

27. Where does the lowest temperature occur in a vapour compression cycle?
(A) Condenser
(B) Evaporator✔
(C) Compressor
(D) Expansion valve

28. 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

29. 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

30. In a domestic vapour compression refrigerator, the refrigerant commonly used is
(A) CO₂
(B) Ammonia
(C) R-12✔
(D) All of these

31. The COP of a vapour compression plant in comparison to vapour absorption plant is
(A) More✔
(B) Less
(C) Same
(D) More/less depending on size of plant

32. The fluids used in Electrolux refrigerator are
(A) Water and hydrogen
(B) Ammonia and hydrogen
(C) Ammonia, water and hydrogen✔
(D) None of these

33. 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✔

34. 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

35. 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

36. 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✔

37. 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

38. During dehumidification process, the relative humidity
(A) Remains constant
(B) Increases
(C) Decreases✔
(D) None of these

39. The refrigerant widely used in domestic refrigerators is
(A) Ammonia
(B) Carbon dioxide
(C) Sulphur dioxide
(D) R-12✔

40. The moisture in a refrigerant is removed by
(A) Evaporator
(B) Safety relief valve
(C) Dehumidifier
(D) Driers✔

41. During sensible cooling of air ________ decreases.
(A) Wet bulb temperature
(B) Relative humidity
(C) Dry bulb temperature✔
(D) Specific humidity

42. 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

43. The wet bulb depression is zero when relative humidity is
(A) Zero
(B) 0.5
(C) 0.75
(D) 1.0✔

44. 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

45. During humidification process, dry bulb temperature
(A) Remains constant✔
(B) Increases
(C) Decreases
(D) None of these

46. The vapour pressure of refrigerant should be
(A) Lower than atmospheric pressure
(B) Higher than atmospheric pressure✔
(C) Equal to atmospheric pressure
(D) Could be anything

47. 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.✔

48. 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✔

49. 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

50. During sensible heating of air _________ decreases.
(A) Wet bulb temperature
(B) Relative humidity✔
(C) Dry bulb temperature
(D) Specific humidity