Refrigeration & Air-Conditioning Practice Set-2

Page 1 of 4

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

None of these

Low pressure vapour refrigerant

Low pressure liquid and vapour refrigerant

High pressure liquid refrigerant

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

Any value

As low as possible (3 to 11°C)

Zero

High, of the order of 25°

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

Is higher than that of the entering air

None of the above

Can be lower or higher than that of the entering air

Is lower than that of the entering air

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

It requires large displacement per TR compared to fluoro carbons.

It is toxic to mucous membranes.

It reacts with copper and its alloys.

All of these

5. 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

6. The optimum effective temperature for human comfort is

Lower in winter than in summer

Same in winter and summer

Higher in winter than in summer

Not dependent on season

7. Reducing suction pressure in refrigeration cycle

Increases power required per ton of refrigeration

Lowers evaporation temperature

All of these

Lowers compressor capacity because vapour is lighter

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

High latent heat of vaporisation

Higher critical temperature

Tow specific heat of liquid

High boiling point

9. The higher temperature in vapour compression cycle occurs at

Compressor discharge

Receiver

Expansion valve

Evaporator

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

Reduced to a value below its critical temperature

Increased to a value above its critical temperature

Equal to critical temperature

None of the above

Page 2 of 4

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

After passing through the expansion or throttle valve

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

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

5 to 7 TR

1 to 3 TR

0.1 to 0.3 TR

3 to 5 TR

13. Formation of frost on evaporator in refrigerator

Can be avoided by proper design

Increases heat transfer rate

Is immaterial

Results in loss of heat due to poor heat transfer

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

All of these

Simple air cooling system

Simple evaporative air cooling system

Bootstrap air cooling system

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

More

Same

Less

None of these

16. 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

None of the above

The moisture present in it begins to condense

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

Low weight per tonne of refrigeration

High heat transfer rate

Low temperature at high altitudes

Higher coefficient of performance

18. 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 + 1

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

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

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

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

Ammonia

Carbon dioxide

Fluorine

Sulphur dioxide

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

More

Less

More/less depending on rating

Same

Page 3 of 4

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

Compressor

Expansion valve

Condenser

Evaporator

22. Critical pressure of a liquid is the pressure

Above which liquid becomes gas

Above which liquid becomes vapour

Above which liquid becomes solid

Above which liquid will remain liquid

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

Discharge pressure

Suction pressure

Back pressure

Critical pressure

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

Between the second heat exchanger and the cooling turbine

Between the secondary compressor and the second heat exchanger

Between the combustion chamber and the first heat exchanger

Between the first heat exchanger and the secondary compressor

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

Smaller/bigger depending on capacity

Bigger

Smaller

Equal

26. The dry bulb temperature during sensible heating of air

Remains constant

Increases

None of these

Decreases

27. Highest pressure encountered in a refrigeration system should be

Critical pressure of refrigerant

Much above critical pressure

Much below critical pressure

Near critical pressure

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

Wet vapour

Saturated liquid

Sub-cooled liquid

Liquid

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

None of these

Wet vapour region

Sub-cooled liquid region

Superheated vapour region

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

Weak solution mixes with strong solution

Ammonia vapour goes into solution

Ammonia vapour is driven out of solution

Page 4 of 4

31. The lowest thermal diffusivity is of

Aluminium

Rubber

Lead

Iron

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

Lithium bromide

R-12

Carbon dioxide

Sulphur dioxide

33. Condensing temperature in a refrigerator is the temperature

Of evaporator

Of cooling medium

Of freezing zone

At which refrigerant gas becomes liquid

34. The COP of a domestic refrigerator

Is less than 1

Is more than 1

Depends upon the make

Is equal to 1

35. Carbon dioxide is

All of these

Odourless

Colourless

Non-flammable

36. During heating and dehumidification process, dry bulb temperature

Increases

None of these

Decreases

Remains constant

37. Vertical lines on pressure-enthalpy chart show constant

Entropy lines

Temperature lines

Pressure lines

Total heat lines

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

Equalize

Reduce

Increase

None of these

39. One ton of the refrigeration is

The cooling effect produced by melting 1 ton of ice

The standard unit used in refrigeration problems

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

40. 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

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