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

1. 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

2. 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

3. The coefficient of performance of Heat Pump is always __________ one.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

4. 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

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

6. 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

7. 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

8. 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

9. 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

10. The COP of a vapour compression plant in comparison to vapour absorption plant is
A. More
B. Less
C. Same
D. More/less depending on size of plant
Answer : A

11. 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

12. 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

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

14. 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

15. The vapour compression refrigerator employs the following cycle
A. Rankine
B. Carnot
C. Reversed Rankine
D. Reversed Carnot
Answer : D

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

17. Vertical lines on pressure-enthalpy chart show constant
A. Pressure lines
B. Temperature lines
C. Total heat lines
D. Entropy lines
Answer : C

18. The human body feels comfortable when the heat stored in the body is
A. Positive
B. Negative
C. Zero
D. None of these
Answer : C

19. The refrigerant supplied to a compressor must be
A. Superheated vapour refrigerant
B. Dry saturated liquid refrigerant
C. A mixture of liquid and vapour refrigerant
D. None of these
Answer : A

20. 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

21. The thermostatic expansion valve operates on the changes in the
A. Degree of superheat at exit from the evaporator
B. Temperature of the evaporator
C. Pressure in the evaporator
D. None of the above
Answer : A

22. 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

23. 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

24. 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

25. The bypass factor for a cooling coil
A. Increases with increase in velocity of air passing through it
B. Decreases with increase in velocity of air passing through it
C. Remains unchanged with increase in velocity of air passing through it
D. May increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering
Answer : A

26. Formation of frost on evaporator in refrigerator
A. Results in loss of heat due to poor heat transfer
B. Increases heat transfer rate
C. Is immaterial
D. Can be avoided by proper design
Answer : A

27. During cooling and dehumidification, dry bulb temperature
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

28. Ammonia absorption refrigeration cycle requires
A. Very little work input
B. Maximum work input
C. Nearly same work input as for vapour compression cycle
D. Zero work input
Answer : A

29. 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

30. 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

31. 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

32. Nusselt number (N_N) is given by
A. N_N = hl/k
B. N_N = ? c_p/k
C. N_N = ? V l /?
D. N_N = V²/t.c_p
Answer : A

33. 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

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

35. Moisture should be removed from refrigerants to avoid
A. Freezing at the expansion valve
B. Restriction to refrigerant flow
C. Corrosion of steel plates
D. All of these
Answer : D

36. The wet bulb temperature during sensible heating of air
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : B

37. The boiling point of ________ is 10.5°C.
A. Ammonia
B. R-12
C. Sulphur dioxide
D. Carbon dioxide
Answer : C

38. For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is ________ that for counter flow.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A

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

40. The wet bulb depression indicates _________ humidity of the air.
A. Absolute
B. Relative
C. Specific
D. None of these
Answer : B

41. 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

42. Critical pressure of a liquid is the pressure
A. Above which liquid will remain liquid
B. Above which liquid becomes gas
C. Above which liquid becomes vapour
D. Above which liquid becomes solid
Answer : A

43. 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

44. Air refrigeration cycle is used in
A. Domestic refrigerators
B. Commercial refrigerators
C. Air conditioning
D. Gas liquefaction
Answer : D

45. 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

46. The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
A. Sub-cooling or under-cooling
B. Super-cooling
C. Normal cooling
D. None of these
Answer : A

47. R-12 is generally preferred over R-22 in deep freezers since
A. It has low operating pressures
B. It gives higher coefficient of performance
C. It is miscible with oil over large range of temperatures
D. All of the above
Answer : C

48. 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

49. The process, generally used in winter air-conditioning to warm and humidity the air, is called
A. Humidification
B. Dehumidification
C. Heating and humidification
D. Cooling and dehumidification
Answer : C

50. Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since
A. These react with water vapour and cause acid rain
B. These react with plants and cause greenhouse effect
C. These react with oxygen and cause its depletion
D. These react with ozone layer
Answer : D