Refrigeration & Air-Conditioning Practice Set-5

Page 1 of 5

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

Copper

Brass

Aluminium

Steel

2. Chaperon equation is applicable for registration at

Saturation point of vapour

Triple point

Sublimation temperature

Saturation point of liquid

3. 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 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

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

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

Vapour absorption cycle

Vapour compression cycle

None of these

Air refrigeration cycle

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

Wet bulb temperature

Dew point temperature

Dry bulb temperature

Relative humidity

6. 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

Wet bulb temperature

Dry bulb temperature

Dew point temperature

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

1 kg of dry air

1 kg of wet air

1 m3 of wet air

1 m3 of dry air

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

Before entering the compressor

After passing through the condenser

Before passing through the condenser

After passing through the expansion or throttle valve

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

None of these

Equal to

Less than

Greater than

10. The specific humidity during cooling and dehumidification

None of these

Remains constant

Increases

Decreases

Page 2 of 5

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

None of these

Equal to

Less than

More than

12. The evaporator used in household refrigerators is

Frosting evaporator

None of these

Non-frosting evaporator

Defrosting evaporator

13. The refrigerant supplied to a compressor must be

Dry saturated liquid refrigerant

None of these

Superheated vapour refrigerant

A mixture of liquid and vapour refrigerant

14. Short horizontal lines on pressure-enthalpy chart show

Constant total heat lines

Constant pressure lines

Constant temperature lines

Constant entropy lines

15. 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

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

Coefficient of performance of refrigeration

Refrigerating efficiency

Relative coefficient of performance

Coefficient of performance of heat pump

17. Air refrigeration cycle is used in

Domestic refrigerators

Gas liquefaction

Air conditioning

Commercial refrigerators

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

1 kg of dry air

1 m3 of dry air

1 kg of wet air

1 m3 of water

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

21 kJ/ min

420 kJ/ min

210 kJ/ min

840 kJ/ min

20. 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

1.25

0.25

0.8

Page 3 of 5

21. 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

22. 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 (T₂ - T₃)] / [T₁ (T₁ - T₂)]

[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]

[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]

[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]

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

50%

10%

25%

75%

24. The desirable property of a refrigerant is

Low boiling point

High latent heat of vaporisation

High critical temperature

All of these

25. The bypass factor for a cooling coil

Increases with increase in velocity of air passing through it

Decreases 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

Remains unchanged with increase in velocity of air passing through it

26. Ammonia is

Highly toxic and inflammable

Non-toxic

Toxic and non-inflammable

Non-inflammable

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

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

28. 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

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

Ammonia and lithium bromide

Water and water

Ammonia and water

Water and lithium bromide

30. 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 1 minute

In 24 hours

Page 4 of 5

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

Power per TR is low

Mass of the refrigeration equipment is low

System has high C.O.P.

Mass of refrigerant circulated in the system is low

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

Brass

Copper

Steel

Aluminium

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

Reduce compressor discharge temperature

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

Reduce compressor overheating

Increase cooling effect

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

Horizontal and uniformly spaced

Curved lines

Horizontal and non-uniformly spaced

Vertical and uniformly spaced

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

Vapour absorption

Carnot cycle

Vapour compression

Electrolux refrigerator

36. The refrigerant for a refrigerator should have

High total heat

High sensible heat

High latent heat

Low latent heat

37. 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

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

Strong solution to ammonia vapour

Strong solution to weak solution

Weak solution to strong solution

Ammonia vapours to weak solution

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

Liquid pump

Absorber and generator

Absorber, generator and liquid pump

Generator

40. 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)

(h1 - h2)/ (hA - h2)

(h2 - hA)/ (h1 - h2)

(hA - h1)/ (h2 - h1)

(hA - h2)/ (h1 - h2)

Page 5 of 5

41. 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.

42. The power per tonne of refrigeration is

3.5 × C.O.P.

None of these

3.5/C.O.P.

C.O.P/3.5

43. The reciprocating refrigerant compressors are very suitable for

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

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

Curved line

Vertical line

Inclined line

Horizontal line

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

1 m3 of water

1 m3 of dry air

1 kg of wet air

1 kg of dry 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