Refrigeration & Air-Conditioning Practice Set-7

Page 1 of 4

1. The lowest temperature during the cycle in a vapour compression system occurs after

Evaporation

Condensation

Expansion

Compression

2. The vertical and uniformly spaced lines on a psychrometric chart indicates

Dry bulb temperature

Dew point temperature

Specific humidity

Wet bulb temperature

3. In a reversed Brayton cycle, the heat is absorbed by the air during

Isentropic compression process

Isentropic expansion process

Constant pressure cooling process

Constant pressure expansion process

4. In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the

Expansion valve to the evaporator

Evaporator to the thermostat

Condenser to the evaporator

Condenser to the expansion valve

5. The difference between dry bulb temperature and dew point temperature, is called

Dry bulb depression

Degree of saturation

Wet bulb depression

Dew point depression

6. In case of sensible cooling of air, the coil efficiency is given by

1 - B.P.F.

B.P.F. - 1

1/ B.P.F.

1 + B.P.F.

7. The horizontal and non-uniformly spaced lines on a psychrometric chart indicates

Dry bulb temperature

Dew point temperature

Wet bulb temperature

Specific humidity

8. In a vapour compression refrigeration system, a throttle valve is used in place of an expander because

The positive work in isentropic expansion of liquid is very small

It improves the C.O.P., as the condenser is small

It considerably reduces mass of the system

It leads to significant cost reduction

9. The relative coefficient of performance is equal to

(Actual C.O.P.) /(Theoretical C.O.P.)

(Actual C.O.P.) × (Theoretical C.O.P.)

None of these

(Theoretical C.O.P.)/ (Actual C.O.P.)

10. A refrigerant compressor is used to

Raise the pressure of the refrigerant

Circulate the refrigerant through the refrigerating system

All of the above

Raise the temperature of the refrigerant

Page 2 of 4

11. In a vapour compression system, the condition of refrigerant is dry saturated vapour

Before entering the compressor

Before entering the condenser

After leaving the compressor

After leaving the condenser

12. The heat rejection factor (HRF) is given by

1 - (1/C.O.P)

1 + (1/C.O.P)

1 - C.O.P.

1 + C.O.P

13. The wet bulb temperature during sensible cooling of air

Decreases

None of these

Increases

Remains constant

14. In aqua ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in

Absorber

Evaporator

Condenser

None of these

15. The refrigerant used in small tonnage commercial machines (hermetically sealed units) is

Sulphur dioxide

R-12

Ammonia

Carbon dioxide

16. A refrigerant with the highest critical pressure is

R-22

R-12

Ammonia

R-11

17. Air refrigerator works on

Both (A) and (B)

(a) Reversed Carnot cycle

(b) Bell Coleman cycle

None of these

18. In order to collect liquid refrigerant and to prevent it from going to a ________, a device known as accumulator is used at the suction of compressor.

Compressor

Evaporator

Expansion valve

Condenser

19. During a refrigeration cycle, heat is rejected by the refrigerant in a

Evaporator

Condenser

Expansion valve

Compressor

20. Which of the following refrigerant is highly toxic and flammable?

R-12

Sulphur dioxide

Carbon dioxide

Ammonia

Page 3 of 4

21. The process, generally used in summer air conditioning to cool and dehumidify the air, is called

Heating and humidification

Dehumidification

Cooling and dehumidification

Humidification

22. The central air conditioning system has ___________ overall efficiency as compared to individual systems.

Higher

None of these

Lower

Same

23. During sensible cooling of air, specific humidity

Decreases

None of these

Increases

Remains constant

24. In a psychrometric chart, specific humidity (moisture content) lines are

Horizontal and non-uniformly spaced

Vertical and uniformly spaced

Horizontal and uniformly spaced

Curved lines

25. The human body feels comfortable when the heat stored in the body is

Zero

None of these

Positive

Negative

26. Moisture should be removed from refrigerants to avoid

Restriction to refrigerant flow

All of these

Freezing at the expansion valve

Corrosion of steel plates

27. The specific humidity during humidification process

Decreases

Increases

Remains constant

None of these

28. The emissivity of a polished silver body is _________ as compared to black body.

Same

Very low

Low

High

29. The leakage in a refrigeration system using ammonia is detected by

All of these

Soap and water

Sulphur sticks

Halide torch

30. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is

Screw

Rotating

Reciprocating

Centrifugal

Page 4 of 4

31. The wet bulb temperature at 100% relative humidity is ________ dry bulb temperature.

None of these

Lower than

Same as

Higher than

32. The dehumidification process, on the psychrometric chart, is shown by

Curved line

Inclined line

Vertical line

Horizontal line

33. Wet bulb temperature is the temperature of air recorded by a thermometer, when

It is not affected by the moisture present in the air

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

None of the above

The moisture present in it begins to condense

34. Most air cooled condensers are designed to operate with a temperature difference of

5°C

14°C

22°C

8°C

35. The undesirable property of a refrigerant is

High boiling point

Non-toxic

Non-explosive

Non-flammable

36. When the air is passed through an insulated chamber having sprays of water maintained at a temperature higher than the dew point temperature of entering air but lower than its dry bulb temperature, then the air is said to be

Heated and humidified

Heated and dehumidified

Cooled and humidified

Cooled and dehumidified

37. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be

3

1/4

4

1/3

38. In mechanical refrigeration system, the refrigerant has the maximum temperature

In evaporator

Between condenser and evaporator

Before expansion valve

Between compressor and condenser

Refrigeration & Air-Conditioning Practice Set-7

Related

Leave a ReplyCancel reply

Secured Payments

Protection

Refrigeration & Air-Conditioning Practice Set-7

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Secured Payments

Protection