Refrigeration & Air-Conditioning Practice Set-5

Page 1 of 5

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

1 kg of dry air

1 m3 of wet air

1 m3 of dry air

1 kg of wet air

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

Reversed Brayton cycle

Reversed Otto cycle

Reversed Carnot cycle

Reversed Joule cycle

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

Bootstrap air cooling system

Regenerative air cooling system

Simple air cooling system

Reduced ambient air cooling system

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

Ammonia

R-12

Sulphur dioxide

Carbon dioxide

5. The refrigerant for a refrigerator should have

High total heat

High latent heat

Low latent heat

High sensible heat

6. The desirable property of a refrigerant is

High latent heat of vaporisation

Low boiling point

High critical temperature

All of these

7. The reciprocating refrigerant compressors are very suitable for

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

8. 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

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

50%

25%

75%

10%

10. Air refrigeration cycle is used in

Commercial refrigerators

Air conditioning

Domestic refrigerators

Gas liquefaction

Page 2 of 5

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

Before entering the expansion valve

Before passing through the condenser

After passing through the condenser

After passing through the expansion or throttle valve

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

Curved line

Vertical line

Inclined line

Horizontal line

13. 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)

(h1 - h2)/ (hA - h2)

(h2 - hA)/ (h1 - h2)

(hA - h1)/ (h2 - h1)

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

1 kg of dry air

1 kg of wet air

1 m3 of water

1 m3 of dry air

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

Coefficient of performance of heat pump

Relative coefficient of performance

Refrigerating efficiency

Coefficient of performance of refrigeration

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

B.P.F. - 1

1/ B.P.F.

1 - B. P.F.

1 + B.P.F.

17. Chaperon equation is applicable for registration at

Triple point

Sublimation temperature

Saturation point of vapour

Saturation point of liquid

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

None of these

Equal to

Greater than

Less than

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

After passing through the condenser

Before entering the compressor

After passing through the expansion or throttle valve

Before passing through the condenser

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

More than

None of these

Less than

Equal to

Page 3 of 5

21. 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)]

[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]

[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]

[T₃ (T₂ - T₃)] / [T₁ (T₁ - T₂)]

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

Dew point temperature

Wet bulb temperature

Dry bulb temperature

Relative humidity

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

210 kJ/ min

840 kJ/ min

21 kJ/ min

420 kJ/ min

24. The refrigerant supplied to a compressor must be

A mixture of liquid and vapour refrigerant

Superheated vapour refrigerant

Dry saturated liquid refrigerant

None of these

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

In 12 hours

In 1 minute

In 1 hour

In 24 hours

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

Mass of refrigerant circulated in the system is low

Power per TR is low

Mass of the refrigeration equipment is low

System has high C.O.P.

28. 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

0.5

0.8

0.25

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

Steel

Copper

Brass

Aluminium

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

Electrolux refrigerator

Vapour compression

Vapour absorption

Carnot cycle

Page 4 of 5

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

Strong solution to ammonia vapour

Weak solution to strong solution

Strong solution to weak solution

Ammonia vapours to weak solution

32. 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

33. The bypass factor for a cooling coil

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

Increases with increase in velocity of air passing through it

34. The specific humidity during cooling and dehumidification

Decreases

Increases

None of these

Remains constant

35. 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

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

Copper

Brass

Steel

Aluminium

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

Horizontal and non-uniformly spaced

Horizontal and uniformly spaced

Curved lines

Vertical and uniformly spaced

38. The evaporator used in household refrigerators is

Non-frosting evaporator

Frosting evaporator

None of these

Defrosting evaporator

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

Ammonia and water

Ammonia and lithium bromide

Water and water

Water and lithium bromide

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

Dry bulb temperature

None of these

Dew point temperature

Wet bulb temperature

Page 5 of 5

41. 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

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

None of these

Vapour absorption cycle

Vapour compression cycle

Air refrigeration cycle

43. Ammonia is

Highly toxic and inflammable

Non-toxic

Toxic and non-inflammable

Non-inflammable

44. Short horizontal lines on pressure-enthalpy chart show

Constant pressure lines

Constant entropy lines

Constant temperature lines

Constant total heat lines

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

Reduces power consumption

Improves C.O.P. of the system

Increases heat transfer

Increases power consumption

Refrigeration & Air-Conditioning Practice Set-5

Related

Leave a ReplyCancel reply

Secured Payments

Protection

Refrigeration & Air-Conditioning Practice Set-5

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Secured Payments

Protection