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

Dew point temperature

None of these

Dry bulb temperature

Wet bulb temperature

2. Chaperon equation is applicable for registration at

Saturation point of vapour

Sublimation temperature

Saturation point of liquid

Triple point

3. 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.

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

Wet bulb temperature

Dry bulb temperature

Dew point temperature

Relative humidity

5. The evaporator used in household refrigerators is

Defrosting evaporator

Frosting evaporator

None of these

Non-frosting evaporator

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

None of these

Less than

Equal to

Greater than

7. The refrigerant for a refrigerator should have

High latent heat

High total heat

Low latent heat

High sensible heat

8. 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?

0.8

0.25

0.5

1.25

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

Water and water

Ammonia and lithium bromide

Ammonia and water

Water and lithium bromide

10. Short horizontal lines on pressure-enthalpy chart show

Constant entropy lines

Constant pressure lines

Constant temperature lines

Constant total heat lines

Page 2 of 5

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

Strong solution to ammonia vapour

Ammonia vapours to weak solution

Strong solution to weak solution

Weak solution to strong solution

12. The specific humidity during cooling and dehumidification

None of these

Increases

Decreases

Remains constant

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

Aluminium

Copper

Brass

Steel

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

Vapour absorption cycle

Air refrigeration cycle

Vapour compression cycle

None of these

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

Curved lines

Vertical and uniformly spaced

Horizontal and non-uniformly spaced

Horizontal and uniformly spaced

16. The desirable property of a refrigerant is

All of these

High latent heat of vaporisation

Low boiling point

High critical temperature

17. 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 - h2)/ (h1 - h2)

(h2 - hA)/ (h1 - h2)

(h1 - h2)/ (hA - h2)

(hA - h1)/ (h2 - h1)

18. The reciprocating refrigerant compressors are very suitable for

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

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

Reversed Carnot cycle

Reversed Brayton cycle

Reversed Otto cycle

Reversed Joule cycle

20. Air refrigeration cycle is used in

Air conditioning

Gas liquefaction

Domestic refrigerators

Commercial refrigerators

Page 3 of 5

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

Horizontal line

Vertical line

Inclined line

Curved line

22. 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

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

Brass

Aluminium

Copper

Steel

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

Sulphur dioxide

Carbon dioxide

R-12

Ammonia

25. 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 mass of water vapour present in 1 kg 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

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

1 m3 of water

1 kg of dry air

1 m3 of dry air

1 kg of wet air

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

420 kJ/ min

840 kJ/ min

21 kJ/ min

210 kJ/ min

28. 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

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

Coefficient of performance of heat pump

Coefficient of performance of refrigeration

Relative coefficient of performance

Refrigerating efficiency

30. The refrigerant supplied to a compressor must be

None of these

Superheated vapour refrigerant

A mixture of liquid and vapour refrigerant

Dry saturated liquid refrigerant

Page 4 of 5

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

System has high C.O.P.

Mass of the refrigeration equipment is low

Mass of refrigerant circulated in the system is low

Power per TR is low

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

Generator

Liquid pump

Absorber, generator and liquid pump

Absorber and generator

33. 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

34. Ammonia is

Non-inflammable

Non-toxic

Highly toxic and inflammable

Toxic and non-inflammable

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

In 1 minute

In 12 hours

In 24 hours

In 1 hour

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

10%

25%

75%

50%

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

Increase cooling effect

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

Reduce compressor overheating

Reduce compressor discharge temperature

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

Reduces power consumption

Increases power consumption

Improves C.O.P. of the system

Increases heat transfer

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

After passing through the expansion or throttle valve

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

40. 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

Page 5 of 5

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

Vapour absorption

Vapour compression

Electrolux refrigerator

Carnot cycle

42. 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 condenser

After passing through the expansion or throttle valve

43. 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)]

[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]

[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]

[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]

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

None of these

More than

Less than

Equal to

45. The bypass factor for a cooling coil

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

Decreases with increase in velocity of air passing through it

Increases with increase in velocity of air passing through it

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