Refrigeration & Air-Conditioning MCQ Solved Paper for LSAT

1. 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

2. 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

3. Highest pressure encountered in a refrigeration system should be
A. Critical pressure of refrigerant
B. Much below critical pressure
C. Much above critical pressure
D. Near critical pressure
Answer : B

4. The C.O.P. of a heat pump working on a reversed Carnot cycle is
A. T?/(T? - T?)
B. (T? - T?)/T?
C. (T? - T?)/T?
D. T?/(T? - T?)
Answer : D

5. 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

6. A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
A. 1 kW
B. 2 kW
C. 3 kW
D. 4 kW
Answer : D

7. The leaks in a refrigeration system using Freon are detected by
A. Halide torch which on detection produces greenish flame lighting
B. Sulphur sticks which on detection gives white smoke
C. Using reagents
D. Smelling
Answer : A

8. 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

9. 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

10. The boiling point of carbon dioxide is
A. -20.5°C
B. -50°C
C. -63.3°C
D. -78.3°C
Answer : D

11. Vapour compression refrigeration is somewhat like
A. Carnot cycle
B. Rankines cycle
C. Reversed Carnot cycle
D. None of the above
Answer : D

12. The reduced ambient air cooling system has
A. One cooling turbine and one heat exchanger
B. One cooling turbine and two heat exchangers
C. Two cooling turbines and one heat exchanger
D. Two cooling turbines and two heat exchangers
Answer : C

13. Moisture in Freon refrigeration system causes
A. Ineffective refrigeration
B. High power consumption
C. Freezing automatic regulating valve
D. Corrosion of whole system
Answer : C

14. 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

15. In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be
A. 0.3
B. 0.6
C. 0.67
D. 1.5
Answer : B

16. 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

17. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is
A. Reciprocating
B. Rotating
C. Centrifugal
D. Screw
Answer : C

18. The sensible heat factor during the heating and humidification process is given by (where h? = Enthalpy of air entering the heating coil, h? = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)
A. (hA - h2)/ (h1 - h2)
B. (h2 - hA)/ (h1 - h2)
C. (h1 - h2)/ (hA - h2)
D. (hA - h1)/ (h2 - h1)
Answer : D

19. One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice
A. In 1 hour
B. In 1 minute
C. In 24 hours
D. In 12 hours
Answer : C

20. 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

21. 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
Answe : D

22. One ton refrigeration corresponds to
A. 50 kcal/ min
B. 50 kcal/ hr
C. 80 kcal/ min
D. 80 kcal/ hr
Answer : A

23. Aqua ammonia is used as refrigerant in the following type of refrigeration system
A. Compression
B. Direct
C. Indirect
D. Absorption
Answer : D

24. 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

25. The refrigerant widely used in domestic refrigerators is
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : D

26. 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)
Answer : C

27. 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

28. The refrigerant for a refrigerator should have
A. High sensible heat
B. High total heat
C. High latent heat
D. Low latent heat
Answer : C

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

30. The specific humidity during heating and humidification process.
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : B

31. The humidity ratio or specific humidity is the mass of water vapour present in
A. 1 m3 of wet air
B. 1 m3 of dry air
C. 1 kg of wet air
D. 1 kg of dry air
Answer : D

32. 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

33. 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

34. 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

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

36. 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

37. 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

38. Which of the following refrigerant has the lowest freezing point?
A. R-11
B. R-12
C. R-22
D. Ammonia
Answer : C

39. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
A. Operating the machine at higher speeds
B. Operating the machine at lower speeds
C. Raising the higher temperature
D. Lowering the higher temperature
Answer : D

40. For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is
A. Zero
B. 20
C. 50
D. 100
Answer : D

41. 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

42. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by
A. Liquid pump
B. Generator
C. Absorber and generator
D. Absorber, generator and liquid pump
Answer : D

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. 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
Answer : C

45. 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

46. While designing the refrigeration system of an aircraft, the prime consideration is that the
A. System has high C.O.P.
B. Power per TR is low
C. Mass of refrigerant circulated in the system is low
D. Mass of the refrigeration equipment is low
Answer : D

47. In vapour compression cycle using NH? 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
Answer : C

48. 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

49. 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

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