Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. Absorption system normally uses the following refrigerant

CO2

Freon-22

Freon-11

Ammonia

2. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

None of these

3. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

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

Expansion valve

Condenser

Compressor

Evaporator

5. During dehumidification process, the relative humidity

Decreases

Increases

None of these

Remains constant

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

Manually operated valve

Electrically operated throttling valve

Thermostatic valve

Capillary tube

7. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

8. During humidification process, dry bulb temperature

Remains constant

None of these

Increases

Decreases

9. Which of the following statement is wrong?

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

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.

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

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

May increase or decrease depending on the type of refrigerant used

Decrease

Remain unaffected

Increase

Page 2 of 4

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

Bright green

Yellow

Red

Orange

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

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

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

High pressure side close to receiver

Suction of compressor

Low pressure side near receiver

Delivery of compressor

14. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

15. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Could be anything

Higher than atmospheric pressure

Equal to atmospheric pressure

16. 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

Wet bulb temperature

Dry bulb temperature

None of these

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

Dehumidification

Humidification

Cooling and dehumidification

Heating and humidification

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

Evaporator

Expansion valve

Condenser

Compressor

19. 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

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

All of these

R-12

Ammonia

CO₂

Page 3 of 4

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

Wet vapour

High pressure saturated liquid

Dry 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

Degree of saturation

Relative humidity

Absolute humidity

Humidity ratio

23. During humidification process, __________ increases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

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

Sulphur sticks which on detection gives white smoke

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

25. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Increases C.O.P

Decreases C.O.P

Other factors decide C.O.P

26. Pick up the incorrect statement

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

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

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

Before passing through the condenser

After passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

28. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Safety relief valve

Driers

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

Increases

Decreases

Depends on other factors

Remain same

30. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

Page 4 of 4

31. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Noisy operation

Very little power consumption

Quiet operation

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

Wet vapour

Saturated liquid

Superheated vapour

Dry saturated vapour

33. 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

34. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

35. 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

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

0.5

0.75

1.0

Zero

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

Less

More/less depending on size of plant

Same

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

Zero

100

39. Which of the following statement is correct?

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.

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

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

40. The refrigerant widely used in domestic refrigerators is

R-12

Sulphur dioxide

Carbon dioxide

Ammonia

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Refrigeration & Air-Conditioning Practice Set-1

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