Refrigeration & Air-Conditioning Practice Set-5

Page 1 of 5

1. The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called

None of these

Dry bulb temperature

Wet bulb temperature

Dew point temperature

2. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by

Generator

Absorber and generator

Absorber, generator and liquid pump

Liquid pump

3. In aqua ammonia and Lithium bromide water absorption refrigeration systems, the refrigerants are respectively

Water and lithium bromide

Ammonia and lithium bromide

Water and water

Ammonia and water

4. For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of

Aluminium

Brass

Steel

Copper

5. The refrigerant for a refrigerator should have

High total heat

Low latent heat

High sensible heat

High latent heat

6. One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice

In 12 hours

In 24 hours

In 1 hour

In 1 minute

7. Air refrigeration cycle is used in

Commercial refrigerators

Gas liquefaction

Air conditioning

Domestic refrigerators

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

Horizontal and non-uniformly spaced

Vertical and uniformly spaced

Horizontal and uniformly spaced

Curved lines

9. The desirable property of a refrigerant is

Low boiling point

All of these

High critical temperature

High latent heat of vaporisation

10. The bypass factor for a cooling coil

Decreases with increase in velocity of air passing through it

Increases with increase in velocity of air passing through it

Remains unchanged with increase in velocity of air passing through it

May increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering

Page 2 of 5

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

1 m3 of dry air

1 kg of dry air

1 kg of wet air

1 m3 of water

12. In vapour compression cycle the condition of refrigerant is superheated vapour

Before entering the expansion valve

After passing through the expansion or throttle valve

After passing through the condenser

Before passing through the condenser

13. The specific humidity during cooling and dehumidification

Decreases

Remains constant

None of these

Increases

14. The refrigerant supplied to a compressor must be

Dry saturated liquid refrigerant

A mixture of liquid and vapour refrigerant

None of these

Superheated vapour refrigerant

15. In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = Bypass factor)

1 - B. P.F.

1/ B.P.F.

1 + B.P.F.

B.P.F. - 1

16. While designing the refrigeration system of an aircraft, the prime consideration is that the

Mass of the refrigeration equipment is low

System has high C.O.P.

Power per TR is low

Mass of refrigerant circulated in the system is low

17. In air-conditioning of aeroplanes, using air as a refrigerant, the cycle used is

Reversed Brayton cycle

Reversed Otto cycle

Reversed Joule cycle

Reversed Carnot cycle

18. Degree of saturation or percentage humidity is

The mass of water vapour present in 1 kg of dry air

The mass of water vapour present in 1 m³ of dry air

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

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

19. Chaperon equation is applicable for registration at

Saturation point of liquid

Sublimation temperature

Saturation point of vapour

Triple point

20. Ammonia is

Highly toxic and inflammable

Toxic and non-inflammable

Non-inflammable

Non-toxic

Page 3 of 5

21. During adiabatic saturation process on unsaturated air __________ remains constant.

Dry bulb temperature

Relative humidity

Dew point temperature

Wet bulb temperature

22. The material of pipe lines for a system using Freon as a refrigerant should be

Copper

Aluminium

Brass

Steel

23. The reciprocating refrigerant compressors are very suitable for

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

24. The power per tonne of refrigeration is

None of these

C.O.P/3.5

3.5 × C.O.P.

3.5/C.O.P.

25. In larger industrial and commercial reciprocating compression systems, refrigerant widely used is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

26. In a refrigerating machine, heat rejected is _________ heat absorbed.

Less than

Greater than

None of these

Equal to

27. Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system

Weak solution to strong solution

Strong solution to weak solution

Ammonia vapours to weak solution

Strong solution to ammonia vapour

28. Most of the domestic refrigerators work on the following refrigeration system

Vapour compression

Vapour absorption

Carnot cycle

Electrolux refrigerator

29. In S.J. unit, one ton of refrigeration is equal to

21 kJ/ min

210 kJ/ min

840 kJ/ min

420 kJ/ min

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

Vertical line

Inclined line

Curved line

Horizontal line

Page 4 of 5

31. The evaporator used in household refrigerators is

Defrosting evaporator

None of these

Non-frosting evaporator

Frosting evaporator

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

1 kg of dry air

1 m3 of dry air

1 m3 of water

1 kg of wet air

33. The ratio of heat extracted in the refrigerator to the work-done on the refrigerant is called

Coefficient of performance of refrigeration

Relative coefficient of performance

Coefficient of performance of heat pump

Refrigerating efficiency

34. In vapour compression cycle the condition off refrigerant is dry saturated vapour

Before passing through the condenser

Before entering the compressor

After passing through the expansion or throttle valve

After passing through the condenser

35. Short horizontal lines on pressure-enthalpy chart show

Constant total heat lines

Constant pressure lines

Constant temperature lines

Constant entropy lines

36. The sensible heat factor during cooling and dehumidification process is given by (where h₁ = Enthalpy of air entering the cooling coil, h₂ = Enthalpy of air leaving the cooling coil, and h_A = Enthalpy of air at the end of dehumidification process)

(hA - h1)/ (h2 - h1)

(h2 - hA)/ (h1 - h2)

(hA - h2)/ (h1 - h2)

(h1 - h2)/ (hA - h2)

37. For unsaturated air, the dew point temperature is __________ wet bulb temperature.

Less than

None of these

More than

Equal to

38. The C.O.P. of an absorption type refrigerator is given by (where T₁ = Temperature at which the working substance receives heat, T₂ = Temperature of cooling water, and T₃ = Evaporator temperature)

[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]

[T₃ (T₂ - T₃)] / [T₁ (T₁ - T₂)]

[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]

[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]

39. Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of C.O.P. of reversed Carnot Cycle?

1.25

0.8

0.5

0.25

40. In which of the following refrigeration system, waste heat can be effectively used?

Vapour absorption cycle

Air refrigeration cycle

None of these

Vapour compression cycle

Page 5 of 5

41. The formation of frost on cooling coils in a refrigerator

Improves C.O.P. of the system

Reduces power consumption

Increases heat transfer

Increases power consumption

42. One of the purposes of sub cooling the liquid refrigerant is to

Reduce compressor overheating

Reduce compressor discharge temperature

Ensure that only liquid and not the vapour enters the expansion (throttling) valve

Increase cooling effect

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

Regenerative air cooling system

Simple air cooling system

Bootstrap air cooling system

Reduced ambient air cooling system

44. Accumulators should have adequate volume to store refrigerant charge at least

75%

50%

10%

25%

45. The humidity ratio or specific humidity is the mass of water vapour present in

1 kg of wet air

1 kg of dry air

1 m3 of dry air

1 m3 of wet air

Refrigeration & Air-Conditioning Practice Set-5

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection

Refrigeration & Air-Conditioning Practice Set-5

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection