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

Thursday 9th of March 2023

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1. 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
Answer : B
2. In a saturated air-water vapour mixture, the
A. Dry bulb temperature is higher than wet bulb temperature
B. Dew point temperature is lower than wet bulb temperature
C. Dry bulb, wet bulb and dew point temperature are same
D. Dry bulb temperature is higher than dew point temperature
Answer : C
3. In a vapour compression system, the condition of refrigerant is dry saturated vapour
A. Before entering the compressor
B. After leaving the compressor
C. Before entering the condenser
D. After leaving the condenser
Answer : A
4. The refrigerant used in small tonnage commercial machines (hermetically sealed units) is
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : C
5. 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
6. 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
7. 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
8. 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
9. Bell Coleman cycle is a
A. Reversed Carnot cycle
B. Reversed Otto cycle
C. Reversed Joule cycle
D. Reversed Rankine cycle
Answer : C
10. 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
11. The difference between dry bulb temperature and dew point temperature, is called
A. Dry bulb depression
B. Wet bulb depression
C. Dew point depression
D. Degree of saturation
Answer : C
12. 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
13. The optimum effective temperature for human comfort is
A. Higher in winter than in summer
B. Lower in winter than in summer
C. Same in winter and summer
D. Not dependent on season
Answer : B
14. The specific humidity during cooling and dehumidification
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C
15. A vapour absorption refrigeration system
A. Gives noisy operation
B. Gives quiet operation
C. Requires little power consumption
D. Cools below 0°C
Answer : B
16. 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
17. The leakage in a refrigeration system using Freon is detected by
A. Halide torch
B. Sulphur sticks
C. Soap and water
D. All of these
Answer : A
18. During sensible cooling of air, specific humidity
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : A
19. 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
20. In aqua ammonia and Lithium bromide water absorption refrigeration systems, the refrigerants are respectively
A. Water and water
B. Water and lithium bromide
C. Ammonia and lithium bromide
D. Ammonia and water
Answer : D
21. 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
22. 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
23. Which of the following statement is wrong?
A. The value of C.O.P. is always greater than one.
B. In a vapour compression system, the condition of refrigerant before entering the compressor is dry saturated vapour.
C. The space between the saturated liquid line and saturated vapour line, in a pressure enthalpy chart, is wet vapour region.
D. None of the above
Answer : D
24. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
A. Automatic expansion valve
B. High side float valve
C. Thermostatic expansion valve
D. Low side float valve
Answer : D
25. The conditioned air supplied to the room must have the capacity to take up
A. Room sensible heat load only
B. Room latent heat load only
C. Both room sensible heat and latent heat loads
D. None of the above
Answer : C
26. 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
27. Which of the following refrigerants has lowest freezing point?
A. Freon-12
B. NH3
C. CO2
D. Freon-22
Answer : D
28. The temperature of ammonia after compression in a vapour compression system is
A. 20 to 50°C
B. 50 to 70°C
C. 70 to 110°C
D. None of these
Answer : C
29. A refrigerant compressor is used to
A. Raise the pressure of the refrigerant
B. Raise the temperature of the refrigerant
C. Circulate the refrigerant through the refrigerating system
D. All of the above
Answer : D
30. The cooling system used for supersonic aircrafts and rockets is
A. Simple air cooling system
B. Bootstrap air cooling system
C. Reduced ambient air cooling system
D. Regenerative air cooling system
Answer : D
31. 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
32. 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
Answer : C
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. 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
35. 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
36. 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
37. 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
38. During cooling and dehumidification, dry bulb temperature
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C
39. Degree of saturation or percentage humidity is
A. The mass of water vapour present in 1 m³ of dry air
B. The mass of water vapour present in 1 kg of dry air
C. 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.
D. 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
Answer : C
40. 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
41. 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
42. 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
43. 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
44. The freezing point of sulphur dioxide is
A. -56.6°C
B. -75.2°C
C. -77.7°C
D. -135.8°C
Answer : B
45. Choose the wrong statement
A. Temperature of medium being cooled must be below that of the evaporator
B. Refrigerant leaves the condenser as liquid
C. All solar thermally operated absorption systems are capable only of intermittent operation
D. Frost on evaporator reduces heat transfer
Answer : A
46. 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
47. The lowest temperature during the cycle in a vapour compression system occurs after
A. Compression
B. Expansion
C. Condensation
D. Evaporation
Answer : D
48. The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner.
A. Same
B. Less
C. More
D. None of these
Answer : B
49. 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
50. 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

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