Refrigeration & Air-Conditioning Practice Set-2

Page 1 of 4

1. In a vapour compression cycle, the refrigerant immediately after expansion valve is

Liquid

Sub-cooled liquid

Saturated liquid

Wet vapour

2. Which of the following refrigerant has the maximum ozone depletion potential in the stratosphere?

Fluorine

Ammonia

Sulphur dioxide

Carbon dioxide

3. Critical pressure of a liquid is the pressure

Above which liquid will remain liquid

Above which liquid becomes vapour

Above which liquid becomes gas

Above which liquid becomes solid

4. In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be

Any value

High, of the order of 25°

As low as possible (3 to 11°C)

Zero

5. Vertical lines on pressure-enthalpy chart show constant

Temperature lines

Entropy lines

Pressure lines

Total heat lines

6. Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.

None of these

Increase

Reduce

Equalize

7. The capacity of a domestic refrigerator is in the range of

0.1 to 0.3 TR

5 to 7 TR

1 to 3 TR

3 to 5 TR

8. During heating and dehumidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

9. Presence of moisture in a refrigerant affects the working of

Condenser

Expansion valve

Evaporator

Compressor

10. One ton of the refrigeration is

The refrigeration effect to produce 1 ton of ice at NTP conditions

The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours

The cooling effect produced by melting 1 ton of ice

The standard unit used in refrigeration problems

Page 2 of 4

11. The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by

(C.O.P)_P = (C.O.P)_R

(C.O.P.)_P = (C.O.P.)_R + 2

(C.O.P)_P = (C.O.P)_R - 1

(C.O.P.)_P = (C.O.P.)_R + 1

12. The higher temperature in vapour compression cycle occurs at

Compressor discharge

Expansion valve

Evaporator

Receiver

13. The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner.

None of these

More

Same

Less

14. The suction pipe diameter of refrigerating unit compressor in comparison to delivery side is

Smaller/bigger depending on capacity

Bigger

Smaller

Equal

15. During heating and humidification, the final relative humidity of air

Can be lower or higher than that of the entering air

Is higher than that of the entering air

None of the above

Is lower than that of the entering air

16. In a bootstrap air evaporative cooling system, the evaporator is provided

Between the second heat exchanger and the cooling turbine

Between the combustion chamber and the first heat exchanger

Between the secondary compressor and the second heat exchanger

Between the first heat exchanger and the secondary compressor

17. In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid

After passing through the expansion or throttle valve

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

18. The evolution of heat of solution takes place in ammonia absorption plant when

Ammonia vapour is driven out of solution

Ammonia vapour goes into solution

Weak solution mixes with strong solution

Ammonia vapour is driven out of solution

19. Formation of frost on evaporator in refrigerator

Can be avoided by proper design

Results in loss of heat due to poor heat transfer

Increases heat transfer rate

Is immaterial

20. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and

R-12

Sulphur dioxide

Lithium bromide

Carbon dioxide

Page 3 of 4

21. The lowest thermal diffusivity is of

Aluminium

Lead

Rubber

Iron

22. In a pressure enthalpy chart, the space to the left of the saturated liquid line represents

Wet vapour region

Sub-cooled liquid region

Superheated vapour region

None of these

23. The optimum effective temperature for human comfort is

Same in winter and summer

Not dependent on season

Higher in winter than in summer

Lower in winter than in summer

24. The dry bulb temperature during sensible heating of air

None of these

Remains constant

Decreases

Increases

25. Which of the following statement is correct for ammonia as a refrigerant?

All of these

It is toxic to mucous membranes.

It requires large displacement per TR compared to fluoro carbons.

It reacts with copper and its alloys.

26. Condensing temperature in a refrigerator is the temperature

At which refrigerant gas becomes liquid

Of freezing zone

Of cooling medium

Of evaporator

27. If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be

More

More/less depending on rating

Same

Less

28. Choose the correct statement

A refrigerant should have low latent heat

Pre-cooling and sub-cooling bf refrigerant are same

Superheat and sensible heat of a refrigerant are same

If operating temperature of system is low, then refrigerant with low boiling point should be used

29. The air cooling system mostly used in transport type aircrafts is

Simple air cooling system

All of these

Simple evaporative air cooling system

Bootstrap air cooling system

30. Highest pressure encountered in a refrigeration system should be

Much above critical pressure

Near critical pressure

Much below critical pressure

Critical pressure of refrigerant

Page 4 of 4

31. A one tonne refrigerating machine means that

One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min

One tonne refrigerant is used

One tonne is the total mass of machine

One tonne of water can be converted into ice

32. In aircraft, air refrigeration Cycle is used because of

Low weight per tonne of refrigeration

Low temperature at high altitudes

Higher coefficient of performance

High heat transfer rate

33. The COP of a domestic refrigerator

Is more than 1

Is less than 1

Depends upon the make

Is equal to 1

34. If a gas is to be liquefied, its temperature must be

Increased to a value above its critical temperature

Reduced to a value below its critical temperature

None of the above

Equal to critical temperature

35. The evaporator changes the low pressure liquid refrigerant from the expansion valve into

High pressure liquid refrigerant

Low pressure vapour refrigerant

Low pressure liquid and vapour refrigerant

None of these

36. Reducing suction pressure in refrigeration cycle

Lowers evaporation temperature

Lowers compressor capacity because vapour is lighter

Increases power required per ton of refrigeration

All of these

37. The pressure at the inlet of a refrigerant compressor is called

Discharge pressure

Critical pressure

Back pressure

Suction pressure

38. Pick up the wrong statement. A refrigerant should have

Higher critical temperature

High boiling point

Tow specific heat of liquid

High latent heat of vaporisation

39. Dry bulb temperature is the temperature of air recorded by a thermometer, when

Its bulb is surrounded by a wet cloth exposed to the air

It is not affected by the moisture present in the air

The moisture present in it begins to condense

None of the above

40. Carbon dioxide is

Non-flammable

All of these

Odourless

Colourless

Refrigeration & Air-Conditioning Practice Set-2

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection

Refrigeration & Air-Conditioning Practice Set-2

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection