Refrigeration & Air-Conditioning Practice Set-2

Page 1 of 4

1. The dry bulb temperature during sensible heating of air

Increases

None of these

Remains constant

Decreases

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

Carbon dioxide

Lithium bromide

Sulphur dioxide

R-12

3. Critical pressure of a liquid is the pressure

Above which liquid becomes vapour

Above which liquid becomes gas

Above which liquid becomes solid

Above which liquid will remain liquid

4. Choose the correct statement

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

A refrigerant should have low latent heat

Pre-cooling and sub-cooling bf refrigerant are same

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

Between the secondary compressor and the second heat exchanger

Between the first heat exchanger and the secondary compressor

Between the second heat exchanger and the cooling turbine

Between the combustion chamber and the first heat exchanger

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

1 to 3 TR

3 to 5 TR

5 to 7 TR

0.1 to 0.3 TR

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

Bigger

Smaller

Equal

Smaller/bigger depending on capacity

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

It is toxic to mucous membranes.

It reacts with copper and its alloys.

All of these

It requires large displacement per TR compared to fluoro carbons.

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

Same

None of these

More

Less

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

Compressor

Condenser

Evaporator

Expansion valve

Page 2 of 4

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

Wet vapour

Liquid

Saturated liquid

Sub-cooled liquid

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

High boiling point

Tow specific heat of liquid

Higher critical temperature

High latent heat of vaporisation

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

Before entering the expansion valve

After passing through the condenser

After passing through the expansion or throttle valve

Before passing through the condenser

14. Carbon dioxide is

Non-flammable

Odourless

Colourless

All of these

15. 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

Ammonia vapour is driven out of solution

Weak solution mixes with strong solution

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

High pressure liquid refrigerant

None of these

Low pressure vapour refrigerant

Low pressure liquid and vapour refrigerant

17. Condensing temperature in a refrigerator is the temperature

Of evaporator

At which refrigerant gas becomes liquid

Of cooling medium

Of freezing zone

18. The COP of a domestic refrigerator

Is more than 1

Is equal to 1

Is less than 1

Depends upon the make

19. One ton of the refrigeration is

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

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

The standard unit used in refrigeration problems

The cooling effect produced by melting 1 ton of ice

20. A one tonne refrigerating machine means that

One tonne of water can be converted into ice

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

Page 3 of 4

21. Reducing suction pressure in refrigeration cycle

Increases power required per ton of refrigeration

All of these

Lowers evaporation temperature

Lowers compressor capacity because vapour is lighter

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

Carbon dioxide

Fluorine

Sulphur dioxide

Ammonia

23. 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 - 1

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

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

High, of the order of 25°

As low as possible (3 to 11°C)

Zero

Any value

25. Highest pressure encountered in a refrigeration system should be

Near critical pressure

Much below critical pressure

Critical pressure of refrigerant

Much above critical pressure

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

More/less depending on rating

More

Same

Less

27. 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

Reduce

Equalize

Increase

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

Critical pressure

Discharge pressure

Suction pressure

Back pressure

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

Is lower than that of the entering air

Can be lower or higher than that of the entering air

Is higher than that of the entering air

None of the above

30. The lowest thermal diffusivity is of

Rubber

Aluminium

Lead

Iron

Page 4 of 4

31. Vertical lines on pressure-enthalpy chart show constant

Temperature lines

Pressure lines

Total heat lines

Entropy lines

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

All of these

Simple evaporative air cooling system

Simple air cooling system

Bootstrap air cooling system

33. 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

The moisture present in it begins to condense

It is not affected by the moisture present in the air

None of the above

34. The optimum effective temperature for human comfort is

Not dependent on season

Lower in winter than in summer

Higher in winter than in summer

Same in winter and summer

35. The higher temperature in vapour compression cycle occurs at

Receiver

Evaporator

Compressor discharge

Expansion valve

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

None of these

Superheated vapour region

Wet vapour region

Sub-cooled liquid region

37. During heating and dehumidification process, dry bulb temperature

Remains constant

None of these

Decreases

Increases

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

Higher coefficient of performance

Low temperature at high altitudes

High heat transfer rate

Low weight per tonne of refrigeration

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

Increased to a value above its critical temperature

None of the above

Equal to critical temperature

Reduced to a value below its critical temperature

40. Formation of frost on evaporator in refrigerator

Is immaterial

Can be avoided by proper design

Increases heat transfer rate

Results in loss of heat due to poor heat transfer

Refrigeration & Air-Conditioning Practice Set-2

Related

Leave a ReplyCancel reply

Secured Payments

Protection

Refrigeration & Air-Conditioning Practice Set-2

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Secured Payments

Protection