Heat Transfer, Refrigeration and Air Conditioning MCQ

Heat Transfer, Refrigeration and Air Conditioning MCQ

01. 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

02. For large tonnage (more than 200 TR) air conditioning applications, the compressor recommended is

C.centrifugal

03. The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.

B.bad

04. Which of the following refrigerant has the lowest boiling point?

B.Carbon dioxide

05. The heat of sun reaches to us according to

C.radiation

6. The most commonly used method for the design of duct size is the

A.static regain method

7. In counter-current flow heat exchangers

A.both the fluids at inlet are in their hottest state

9. The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called

A.Newton's law of cooling

10. The pressure at the inlet of a refrigerant compressor is called

A.suction pressure

11. The process, generally used in summer air conditioning to cool and dehumidify the air, is called

A.cooling and dehumidification

12. The leakage in a refrigeration system using ammonia is detected by

A. Sulphur sticks

13. The lowest temperature during the cycle in a vapour compression system occurs after

A.evaporation

14. The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity)

A.22°C DBT and 60% RH

15. The dry bulb temperature lines, on the psychrometric chart are

A.vertical and uniformly spaced

16. The pressure at the outlet of a refrigerant compressor is called

A.discharge pressure

17. A simple air cooling system is good for __________ flight speeds.

A.low

18. _________is the process of removing water vapour from the surrounding air.

A. Dehydration

19. The cooling of air, without any change in its specific humidity, is known as ___________

A. sensible cooling.

20. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called

A.saturated air

21. The ____________in a refrigerator controls the flow of refrigerant.

A. expansion valve

22. The relative humidity lines on a psychrometric chart are

A.curved lines

23. The humidification process, on the psychrometric chart is shown by

Ans. vertical line

24. The horizontal and nonuniformly spaced lines on a psychrometric chart indicates

Ans. dew point temperature

25. The inclined and non-uniformly spaced straight lines on a psychrometric chart indicates

Ans. wet bulb temperature.

26. A vapour absorption refrigeration system

Ans. gives quiet operation

27. The rato of energy transferred by convection to that by conduction is called

Ans. Nusselt number

28. Wet bulb temperature indicates the.

Ans. moisture content in air

29. The heat is transferred by conduction, convection and radiation in

Ans. boiler furnaces

30. A grey body is one whose absorptivity does not vary with

Ans. temperature and wave length of the incident ray.

31. Hydrogen is used in electrolux refrigeration system so as to __________ the rate of evaporation of the liquid ammonia passing through the evaporator.

Ans. increase

32. Dry bulb temperature is the temperature of air recorded by a thermometer, when

Ans. it is not affected by the moisture present in the air

33. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called

Ans. low side float valve

34. The emissivity of a polished silver body is __________ as compared to black body.

Ans. very low

35. R-11 has the

Ans. highest critical point temperature.  

36. Air refrigerator works on

Ans. reversed Carnot cycle

B.Bell Coleman cycle

Ans. both (a) and (b)

37. The boiling point of carbon dioxide is

Ans.-78.3°C

38. The mass of water vapour present in __________ is called absolute humidity.

Ans.1 m3 of dry air

39. The relative coefficient of performance is equal to

Ans. theoretical c.o.p/ actual c.o.p

40. The cooling system used for supersonic aircrafts and rockets is

Ans. regenerative air cooling system

41. The desirable property of a refrigerant is

A.low boiling point

B.high critical temperature

C.high latent heat of vaporisation

Ans.all of these

42. The colour of the flame of halide torch, in case of leakage of freon refrigerant, will change to

Ans. bright green

43. The wet bulb depression indicates __________ humidity of the air.

B.relative

44. The refrigerant widely used in domestic refrigerators is

D.R-12

45. When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmittivity (τ) = 0, then the body is said to be a

A. black body

46. In a vapour compression system, the condition of refrigerant before passing through the condenser is

Ans. superheated vapour

47. The critical temperature is the temperature

Ans. above which a gas will never liquified

48. The evaporator changes the low pressure liquid refrigerant from the expansion valve into

Ans. low pressure vapour refrigerant

49. The mass of water vapour present in 1 kg of dry air, is called humidity ratio.

Ans. True

50. Most thermostatic expansion

valves are set for a superheat of

Ans.5°C

 

 For download PDF Click Here