Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Lower than atmospheric pressure

Could be anything

Higher than atmospheric pressure

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

Halide torch which on detection produces greenish flame lighting

Using reagents

Sulphur sticks which on detection gives white smoke

Smelling

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

Suction of compressor

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

4. During humidification process, __________ increases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

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

Expansion valve

Condenser

Compressor

Evaporator

6. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

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

Evaporator

Compressor

Expansion valve

Condenser

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

Ammonia

R-12

All of these

CO₂

9. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

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

Depends on other factors

Increases

Decreases

Remain same

Page 2 of 4

11. During humidification process, dry bulb temperature

Decreases

Increases

None of these

Remains constant

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

Manually operated valve

Capillary tube

Thermostatic valve

Electrically operated throttling valve

13. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Wet bulb temperature

Relative humidity

14. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Safety relief valve

Evaporator

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

Higher

Lower

None of these

Same

16. 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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

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

Zero

100

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

Same

Less

More/less depending on size of plant

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

Yellow

Red

Orange

Bright green

20. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

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

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

Page 3 of 4

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

Wet bulb temperature

None of these

Dew point temperature

Dry bulb temperature

22. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

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

Very wet vapour

Wet vapour

High pressure saturated liquid

Dry vapour

24. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Very little power consumption

Quiet operation

Noisy operation

25. During dehumidification process, the relative humidity

Remains constant

Increases

None of these

Decreases

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

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

27. Which of the following statement is wrong?

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

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

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.

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

Saturated liquid

Superheated vapour

Wet vapour

Dry saturated vapour

29. 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

30. During sensible cooling of air ________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

Page 4 of 4

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

0.5

0.75

1.0

Zero

32. Under cooling in a refrigeration cycle

Increases C.O.P

Other factors decide C.O.P

Decreases C.O.P

C.O.P remains unaltered

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

Slightly above atmospheric pressure

56 bars

Atmospheric pressure

24 bars

34. One ton refrigeration corresponds to

50 kcal/ min

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

35. 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

Degree of saturation

Relative humidity

Absolute humidity

Humidity ratio

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

Heating and humidification

Cooling and dehumidification

Humidification

Dehumidification

37. Which of the following statement is correct?

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

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

38. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Sulphur dioxide

Carbon dioxide

39. Absorption system normally uses the following refrigerant

Freon-22

Ammonia

CO2

Freon-11

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

After passing through the expansion throttle valve

Before entering the expansion valve

After passing through the condenser

Before passing through the condenser

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Refrigeration & Air-Conditioning Practice Set-1

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