SSC JE - Refrigeration & Air-Conditioning 1000+ MCQ [Solved] PDF Download

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

2. A bootstrap air cooling system has
A. One heat exchanger
B. Two heat exchangers
C. Three heat exchangers
D. Four heat exchangers
Answer : B

3. 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

4. Which of the following refrigerants has lowest freezing point?
A. Freon-12
B. NH3
C. CO2
D. Freon-22
Answer : D

5. 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

6. In vapour compression cycle, the condition of refrigerant is very wet 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

7. The capillary tube, as an expansion device, is used in
A. Domestic refrigerators
B. Water coolers
C. Room air conditioners
D. All of these
Answer : D

8. 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

9. In a vapour compression refrigeration system, a throttle valve is used in place of an expander because
A. It considerably reduces mass of the system
B. It improves the C.O.P., as the condenser is small
C. The positive work in isentropic expansion of liquid is very small
D. It leads to significant cost reduction
Answer : C

10. 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

11. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The bypass factor of the heating coil is
A. 0.376
B. 0.4
C. 0.6
D. 0.67
Answer : C

12. 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

13. The Freon group of refrigerants are
A. Halocarbon refrigerants
B. Zoetrope refrigerants
C. Inorganic refrigerants
D. Hydrocarbon refrigerants
Answer : A

14. The specific humidity during cooling and dehumidification
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

15. 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

16. The central air conditioning system has ________ overall efficiency as compared to individual systems.
A. Same
B. Lower
C. Higher
D. None of these
Answer : C

17. 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

18. Which of the following refrigerant has the lowest boiling point?
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : B

19. A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is
A. Ammonia
B. Carbon dioxide
C. Freon
D. Brine
Answer : B

20. 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

21. An evaporator is also known as
A. Freezing coil
B. Cooling coil
C. Chilling coil
D. All of these
Answer : D

22. 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

23. 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

24. 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

25. The capillary tube is not used in large capacity refrigeration systems because
A. Cost is too high
B. Capacity control is not possible
C. It is made of copper
D. Required pressure drop cannot be achieved
Answer : B

26. Which of the following is not a desirable property of a refrigerant?
A. High risibility with oil
B. Low boiling point
C. Good electrical conductor
D. Large latent heat
Answer : C

27. 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

28. 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

29. A vapour absorption refrigerator uses __________ as a refrigerant.
A. Water
B. Ammonia
C. Freon
D. Aqua-ammonia
Answer : D

30. During humidification process, __________ increases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : B

31. The alignment circle is marked on the psychrometric chart at
A. 20°C DBT and 50% RH
B. 26°C DBT and 50% RH
C. 20°C DBT and 60% RH
D. 26°C DBT and 60% RH
Answer : B

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. 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

34. 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

35. A one tonne refrigerating machine means that
A. One tonne is the total mass of machine
B. One tonne refrigerant is used
C. One tonne of water can be converted into ice
D. One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
Answer : D

36. 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

37. Wet bulb temperature is the temperature of air recorded by a thermometer, when
A. It is not affected by the moisture present in the air
B. Its bulb is surrounded by a wet cloth exposed to the air
C. The moisture present in it begins to condense
D. None of the above
Answer : B

38. The unit of thermal diffusivity is
A. m/hK
B. m/h
C. m²/h
D. m²/hK
Answer : C

39. Presence of moisture in a refrigerant affects the working of
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : D

40. One ton of the refrigeration is
A. The standard unit used in refrigeration problems
B. The cooling effect produced by melting 1 ton of ice
C. The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours
D. The refrigeration effect to produce 1 ton of ice at NTP conditions
Answer : C

41. 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

42. A refrigerant with the highest critical pressure is
A. R-11
B. R-12
C. R-22
D. Ammonia
Answer : D

43. 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

44. 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
Answer : D

45. 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

46. 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

47. 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

48. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called
A. Dry air
B. Moist air
C. Saturated air
D. Specific humidity
Answer : C

49. Most thermostatic expansion valves are set for a superheat of
A. 5°C
B. 10°C
C. 15°C
D. 20°C
Answer : A

50. The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.
A. More
B. Less
C. Equally
D. Unpredictable
Answer : A