Refrigeration & Air-Conditioning Practice Set-5

Page 1 of 5

1. Chaperon equation is applicable for registration at

Saturation point of liquid

Triple point

Sublimation temperature

Saturation point of vapour

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

After passing through the expansion or throttle valve

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

3. 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

Refrigerating efficiency

Coefficient of performance of heat pump

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

Copper

Aluminium

Steel

Brass

5. The power per tonne of refrigeration is

C.O.P/3.5

3.5/C.O.P.

None of these

3.5 × C.O.P.

6. The bypass factor for a cooling coil

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

Decreases with increase in velocity of air passing through it

7. The evaporator used in household refrigerators is

None of these

Defrosting evaporator

Frosting evaporator

Non-frosting evaporator

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

Horizontal line

Curved line

Vertical line

Inclined line

9. Short horizontal lines on pressure-enthalpy chart show

Constant pressure lines

Constant temperature lines

Constant total heat lines

Constant entropy lines

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

1 + B.P.F.

B.P.F. - 1

1 - B. P.F.

1/ B.P.F.

Page 2 of 5

11. Ammonia is

Non-inflammable

Non-toxic

Toxic and non-inflammable

Highly toxic and inflammable

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

Steel

Copper

Aluminium

Brass

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

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

Reduce compressor overheating

Increase cooling effect

Reduce compressor discharge temperature

14. The refrigerant for a refrigerator should have

High latent heat

Low latent heat

High sensible heat

High total heat

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

Ammonia and lithium bromide

Water and water

Water and lithium bromide

Ammonia and water

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

Horizontal and uniformly spaced

Horizontal and non-uniformly spaced

Curved lines

Vertical and uniformly spaced

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

420 kJ/ min

21 kJ/ min

840 kJ/ min

210 kJ/ min

18. 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)

(h2 - hA)/ (h1 - h2)

(hA - h1)/ (h2 - h1)

(hA - h2)/ (h1 - h2)

(h1 - h2)/ (hA - h2)

19. 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?

0.5

0.8

0.25

1.25

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

1 m3 of dry air

1 kg of wet air

1 kg of dry air

1 m3 of water

Page 3 of 5

21. The reciprocating refrigerant compressors are very suitable for

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

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

Increases power consumption

Reduces power consumption

Improves C.O.P. of the system

Increases heat transfer

23. 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

24. The desirable property of a refrigerant is

Low boiling point

High latent heat of vaporisation

High critical temperature

All of these

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

None of these

Less than

Greater than

Equal to

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

Before passing through the condenser

After passing through the condenser

Before entering the compressor

After passing through the expansion or throttle valve

27. 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 wet air

1 m3 of dry air

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

Bootstrap air cooling system

Reduced ambient air cooling system

Regenerative air cooling system

Simple air cooling system

29. 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

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

Reversed Brayton cycle

Reversed Joule cycle

Reversed Otto cycle

Reversed Carnot cycle

Page 4 of 5

31. The refrigerant supplied to a compressor must be

Superheated vapour refrigerant

None of these

A mixture of liquid and vapour refrigerant

Dry saturated liquid refrigerant

32. 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

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

50%

75%

10%

25%

34. 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)

[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]

[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]

[T₃ (T₂ - T₃)] / [T₁ (T₁ - T₂)]

[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]

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

Relative humidity

Dew point temperature

Dry bulb temperature

Wet bulb temperature

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

R-12

Carbon dioxide

Ammonia

Sulphur dioxide

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

Mass of the refrigeration equipment is low

Power per TR is low

System has high C.O.P.

Mass of refrigerant circulated in the system is low

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

Liquid pump

Absorber, generator and liquid pump

Absorber and generator

Generator

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

In 12 hours

In 1 hour

In 24 hours

In 1 minute

40. Air refrigeration cycle is used in

Domestic refrigerators

Gas liquefaction

Commercial refrigerators

Air conditioning

Page 5 of 5

41. Degree of saturation or percentage humidity is

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

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 mass of water vapour present in 1 kg of dry air

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

Vapour compression cycle

Air refrigeration cycle

Vapour absorption cycle

None of these

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

None of these

Equal to

More than

Less than

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

Carnot cycle

Electrolux refrigerator

Vapour compression

Vapour absorption

45. The specific humidity during cooling and dehumidification

Increases

Decreases

None of these

Remains constant

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