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

1. 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

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

3. 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

4. In a refrigeration system, heat absorbed in comparison to heat rejected is
A. More
B. Less
C. Same
D. More for small capacity and less for high capacity
Answer : B

5. 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

6. 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

7. 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

8. 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

9. The index which correlates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as
A. Mean radiant temperature
B. Effective temperature
C. Dew point temperature
D. None of these
Answer : B

10. In larger industrial and commercial reciprocating compression systems, refrigerant widely used is
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : A

11. 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
Answer : B

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

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

14. 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

15. When the temperature of the surrounding is higher than the temperature of the body, then the heat loss by convection from the body to the surrounding will be
A. Positive
B. Negative
C. Zero
D. None of these
Answer : B

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

17. The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called
A. Kinetic theory of gases
B. Newton's law of gases
C. Dalton's law of partial pressures
D. Avogadro's hypothesis
Answer : C

18. 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

19. The evaporator used in household refrigerators is
A. Frosting evaporator
B. Non-frosting evaporator
C. Defrosting evaporator
D. None of these
Answer : A

20. 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

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

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

23. 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

24. 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

25. 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
Answer : D

26. Air refrigerator works on
A. Reversed Carnot cycle
B. Bell Coleman cycle
C. Both (A) and (B)
D. None of these
Answer : C

27. 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

28. 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
Answer : C

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

31. 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

32. 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

33. When the air is passed through an insulated chamber having sprays of water maintained at a temperature higher than the dew point temperature of entering air but lower than its dry bulb temperature, then the air is said to be
A. Cooled and humidified
B. Cooled and dehumidified
C. Heated and humidified
D. Heated and dehumidified
Answer : A

34. 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

35. 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

36. In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = Bypass factor)
A. B.P.F. - 1
B. 1 - B. P.F.
C. 1/ B.P.F.
D. 1 + B.P.F.
Answer : B

37. 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

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

39. 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

40. Which of the following statement is correct?
A. The human body can lose heat even if its temperature is less than the atmospheric temperature.
B. The increase in air movement increases the evaporation from the human body.
C. The warm air increases the rate of radiation of heat from the human body.
D. Both (A) and (B)
Answer : D

41. In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to
A. Collect liquid refrigerant and prevent it from going to compressor
B. Detect liquid in vapour
C. Superheat the vapour
D. Collect vapours
Answer : A

42. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg)
A. 25 kJ/kg
B. 50 kJ/kg
C. 100 kJ/kg
D. 125 kJ/kg
Answer : B

43. Rating of a domestic refrigerator is of the order of
A. 0.1 ton
B. 5 tons
C. 10 tons
D. 40 tons
Answer : A

44. The desirable property of a refrigerant is
A. Low boiling point
B. High critical temperature
C. High latent heat of vaporisation
D. All of these
Answer : D

45. 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

46. In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is
A. High pressure saturated liquid
B. Wet vapour
C. Very wet vapour
D. Dry vapour
Answer : A

47. 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

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

49. Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system
A. Strong solution to weak solution
B. Weak solution to strong solution
C. Strong solution to ammonia vapour
D. Ammonia vapours to weak solution
Answer : B

50. The thermostatic expansion valve is used in __________ type of evaporators.
A. Flooded
B. DX coil
C. Dry
D. None of these
Answer : C