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Refrigeration & Air-Conditioning 1000+ MCQ with answer for NEET

Thursday 9th of March 2023

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1. During sensible cooling,
A. Relative humidity remains constant
B. Wet bulb temperature increases
C. Specific humidity increases
D. Partial pressure of vapour remains constant
Answer : D
2. 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
3. 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
4. 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
5. In a vapour compression cycle, the refrigerant immediately after expansion valve is
A. Liquid
B. Sub-cooled liquid
C. Saturated liquid
D. Wet vapour
Answer : D
6. The leakage in a refrigeration system using ammonia is detected by
A. Halide torch
B. Sulphur sticks
C. Soap and water
D. All of these
Answer : B
7. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
A. Heated and dehumidified
B. Heated and humidified
C. Cooled and humidified
D. Cooled and dehumidified
Answer : B
8. 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
9. The higher temperature in vapour compression cycle occurs at
A. Receiver
B. Expansion valve
C. Evaporator
D. Compressor discharge
Answer : D
10. During a refrigeration cycle, heat is rejected by the refrigerant in a
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : B
11. 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
Answer : B
12. The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity)
A. 25°C DBT and 100% RH
B. 20°C DBT and 80% RH
C. 22°C DBT and 60% RH
D. 25°C DBT and 40% RH
Answer : C
13. 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
14. 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
15. During humidification process, __________ increases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : B
16. The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by
A. (C.O.P.)P = (C.O.P.)R + 2
B. (C.O.P.)P = (C.O.P.)R + 1
C. (C.O.P)P = (C.O.P)R - 1
D. (C.O.P)P = (C.O.P)R
Answer : B
17. 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
18. The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is
A. Same
B. More
C. Less
D. More or less depending on ambient conditions
Answer : C
19. An evaporator is also known as
A. Freezing coil
B. Cooling coil
C. Chilling coil
D. All of these
Answer : D
20. The moisture in a refrigerant is removed by
A. Evaporator
B. Safety relief valve
C. Dehumidifier
D. Driers
Answer : D
21. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is
A. Reciprocating
B. Rotating
C. Centrifugal
D. Screw
Answer : C
22. In aircraft, air refrigeration Cycle is used because of
A. Low weight per tonne of refrigeration
B. High heat transfer rate
C. Low temperature at high altitudes
D. Higher coefficient of performance
Answer : A
23. The heat rejection factor (HRF) is given by
A. 1 + C.O.P
B. 1 - C.O.P.
C. 1 + (1/C.O.P)
D. 1 - (1/C.O.P)
Answer : C
24. 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
25. 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
26. 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
27. 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
28. An Electrolux refrigerator is called a __________ absorption system.
A. Single fluid
B. Two fluids
C. Three fluids
D. None of these
Answer : C
29. For unsaturated air, the dew point temperature is __________ wet bulb temperature.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : B
30. During sensible heating of air _________ decreases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : B
31. If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be
A. Same
B. More
C. Less
D. More/less depending on rating
Answer : B
32. The evaporator used in household refrigerators is
A. Frosting evaporator
B. Non-frosting evaporator
C. Defrosting evaporator
D. None of these
Answer : A
33. 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
34. 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
35. 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
Answer : A
36. The boiling point of ammonia is
A. 100°C
B. 50°C
C. 33.3°C
D. 0°C
Answer : C
37. 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
38. 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
39. 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
40. Mass flow ratio of NH? in comparison to Freon12 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
Answer : B
41. 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
42. Choose the correct statement
A. A refrigerant should have low latent heat
B. If operating temperature of system is low, then refrigerant with low boiling point should be used
C. Pre-cooling and sub-cooling bf refrigerant are same
D. Superheat and sensible heat of a refrigerant are same
Answer : B
43. 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
44. 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
45. One ton refrigeration corresponds to
A. 50 kcal/ min
B. 50 kcal/ hr
C. 80 kcal/ min
D. 80 kcal/ hr
Answer : A
46. 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
47. 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
48. Presence of moisture in a refrigerant affects the working of
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : D
49. 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
50. The ratio of heat extracted in the refrigerator to the work-done on the refrigerant is called
A. Coefficient of performance of refrigeration
B. Coefficient of performance of heat pump
C. Relative coefficient of performance
D. Refrigerating efficiency
Answer : A

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