Refrigeration & Air-Conditioning Practice Set-1

Published May 16, 2021 · Updated May 16, 2021

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

Wet vapour

Dry saturated vapour

Superheated vapour

Saturated liquid

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

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

24 bars

3. Which of the following statement is wrong?

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.

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.

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

Remain unaffected

Increase

Decrease

May increase or decrease depending on the type of refrigerant used

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

Less

More/less depending on size of plant

Same

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

Delivery of compressor

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

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

Increases

Remain same

Decreases

Depends on other factors

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

None of these

Wet bulb temperature

Dry bulb temperature

Dew point temperature

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

Zero

100

10. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Noisy operation

Very little power consumption

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11. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Ammonia, water and hydrogen

Water and hydrogen

None of these

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

Bright green

Orange

Yellow

Red

13. During dehumidification process, the relative humidity

Remains constant

Increases

None of these

Decreases

14. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

15. Absorption system normally uses the following refrigerant

Freon-22

CO2

Freon-11

Ammonia

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

None of these

Same

Lower

Higher

17. During sensible cooling of air ________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

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

Cooling and dehumidification

Humidification

Heating and humidification

Dehumidification

19. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Decreases C.O.P

Other factors decide C.O.P

Increases C.O.P

20. During humidification process, dry bulb temperature

Increases

Remains constant

Decreases

None of these

Page 3 of 4

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

High pressure saturated liquid

Dry vapour

Wet vapour

Very wet vapour

22. 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

Degree of saturation

Absolute humidity

Relative humidity

23. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Equal to atmospheric pressure

Lower than atmospheric pressure

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

All of these

Ammonia

CO₂

R-12

25. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Dehumidifier

Evaporator

26. During humidification process, __________ increases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

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

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

After passing through the expansion throttle valve

28. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

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

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

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

Compressor

Evaporator

Condenser

Expansion valve

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

Manually operated valve

Thermostatic valve

Electrically operated throttling valve

Capillary tube

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

Expansion valve

Compressor

Evaporator

Condenser

33. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Ammonia

Sulphur dioxide

R-12

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

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

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

0.75

0.5

1.0

Zero

36. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

37. Pick up the incorrect statement

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

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

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

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

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Smaller cabinet should be used

39. Which of the following statement is correct?

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

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

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

All of these

40. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

Refrigeration & Air-Conditioning Practice Set-1

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