Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. During humidification process, __________ increases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

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

Zero

0.75

1.0

0.5

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

Zero

100

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

Remain same

Increases

Depends on other factors

Decreases

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

Evaporator

Compressor

Expansion valve

Condenser

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

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

Cooling and dehumidification

Heating and humidification

Dehumidification

Humidification

8. 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

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

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

Capillary tube

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

Lower

Same

Higher

None of these

Page 2 of 4

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

56 bars

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

12. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

Water and hydrogen

None of these

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

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

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

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

15. Absorption system normally uses the following refrigerant

CO2

Freon-11

Ammonia

Freon-22

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

Very wet vapour

High pressure saturated liquid

Wet vapour

Dry vapour

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

Ammonia

CO₂

R-12

All of these

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

After passing through the condenser

Before passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

19. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

20. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Page 3 of 4

21. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

Absolute humidity

Relative humidity

Humidity ratio

Degree of saturation

23. During dehumidification process, the relative humidity

None of these

Decreases

Increases

Remains constant

24. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

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

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

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

Yellow

Bright green

Orange

Red

27. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ hr

50 kcal/ min

80 kcal/ hr

28. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

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

Dry bulb temperature

Wet bulb temperature

Dew point temperature

None of these

30. Which of the following statement is correct?

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

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.

Page 4 of 4

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

More/less depending on size of plant

Same

Less

32. Pick up the incorrect statement

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

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

33. During humidification process, dry bulb temperature

Decreases

None of these

Increases

Remains constant

34. 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.

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

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

35. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Noisy operation

Very little power consumption

36. During sensible heating of air _________ decreases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

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

Condenser

Compressor

Evaporator

Expansion valve

38. 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

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

Decrease

May increase or decrease depending on the type of refrigerant used

Remain unaffected

Increase

40. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Driers

Safety relief valve

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Refrigeration & Air-Conditioning Practice Set-1

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