Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. The COP of a vapour compression plant in comparison to vapour absorption plant is

Same

More/less depending on size of plant

Less

2. For air conditioning the operation theater in a hospital, the percentage of outside air in the air supplied is

100

Zero

3. Where does the lowest temperature occur in a vapour compression cycle?

Expansion valve

Condenser

Compressor

Evaporator

4. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

5. In vapour compression cycle, the condition of refrigerant is saturated liquid

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

After passing through the expansion throttle valve

6. In a refrigeration cycle, the flow of refrigerant is controlled by

Evaporator

Compressor

Expansion valve

Condenser

7. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant

Increases

Remain same

Depends on other factors

Decreases

8. In a vapour compression system, the condition of refrigerant before passing through the condenser is

Wet vapour

Saturated liquid

Dry saturated vapour

Superheated vapour

9. Allowable pressure on high pressure side or ammonia absorption system is of the order of

Slightly above atmospheric pressure

24 bars

56 bars

Atmospheric pressure

10. In vapour compression cycle using NH₃ as refrigerant, initial charge is filled at

Suction of compressor

Low pressure side near receiver

Delivery of compressor

High pressure side close to receiver

Page 2 of 4

11. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called

Dew point temperature

None of these

Dry bulb temperature

Wet bulb temperature

12. During humidification process, __________ increases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

13. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Noisy operation

Quiet operation

Very little power consumption

14. 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, is called

Humidity ratio

Absolute humidity

Relative humidity

Degree of saturation

15. The centrifugal compressors are generally used for refrigerants that require

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

16. In a domestic vapour compression refrigerator, the refrigerant commonly used is

All of these

CO₂

Ammonia

R-12

17. Which of the following statement is correct?

All of these

In vapour absorption refrigerator, the compression of refrigerant is avoided.

In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.

Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.

18. The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is

Wet vapour

Very wet vapour

High pressure saturated liquid

Dry vapour

19. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ min

80 kcal/ hr

50 kcal/ min

20. During dehumidification process, the relative humidity

Increases

None of these

Remains constant

Decreases

Page 3 of 4

21. The leaks in a refrigeration system using Freon are detected by

Halide torch which on detection produces greenish flame lighting

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

22. Which of the following statement is wrong?

In vapour compression cycle, the useful part of the heat transfer is at the condenser.

In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.

23. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

24. The process, generally used in winter air-conditioning to warm and humidity the air, is called

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

25. The moisture in a refrigerant is removed by

Dehumidifier

Driers

Evaporator

Safety relief valve

26. Domestic refrigerator working on vapour compression cycle uses the following type of expansion device

Electrically operated throttling valve

Manually operated valve

Capillary tube

Thermostatic valve

27. Absorption system normally uses the following refrigerant

CO2

Freon-11

Freon-22

Ammonia

28. The colour of the flame of halide torch, in case of leakage of Freon refrigerant, will change to

Orange

Red

Yellow

Bright green

29. During humidification process, dry bulb temperature

Decreases

Remains constant

None of these

Increases

30. The C.O.P. of a Carnot refrigerator in winter will be _________ as compared to C.O.P. in summer.

None of these

Lower

Higher

Same

Page 4 of 4

31. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Increases C.O.P

Other factors decide C.O.P

Decreases C.O.P

32. The C.O.P of a refrigeration cycle with increase in evaporator temperature, keeping condenser temperature constant, will

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

Remain unaffected

33. The wet bulb depression is zero when relative humidity is

1.0

0.75

Zero

0.5

34. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Sulphur dioxide

Carbon dioxide

35. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

36. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Higher than atmospheric pressure

37. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

38. Pick up the incorrect statement

A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

Lithium bromide plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

39. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

40. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia and hydrogen

Ammonia, water and hydrogen

None of these

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Refrigeration & Air-Conditioning Practice Set-1

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