Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

2. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

3. During humidification process, __________ increases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

4. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

5. During humidification process, dry bulb temperature

Increases

Remains constant

Decreases

None of these

6. Which of the following statement is wrong?

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

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.

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

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

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

1.0

Zero

0.75

0.5

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

Humidification

Dehumidification

Heating and humidification

Cooling and dehumidification

10. 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

Page 2 of 4

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

Compressor

Evaporator

Condenser

Expansion valve

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

Electrically operated throttling valve

Thermostatic valve

Capillary tube

Manually operated valve

13. 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

Bigger cabinet should be used

Perfectly tight vapour seal should be used

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

Orange

Yellow

Red

Bright green

15. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Evaporator

Dehumidifier

16. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

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

After passing through the condenser

After passing through the expansion throttle valve

Before passing through the condenser

Before entering the expansion valve

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

Dry saturated vapour

Wet vapour

Saturated liquid

Superheated vapour

19. 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

Relative humidity

Degree of saturation

Absolute humidity

Humidity ratio

20. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia and hydrogen

Ammonia, water and hydrogen

Page 3 of 4

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

All of these

Ammonia

R-12

CO₂

22. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Very little power consumption

Quiet operation

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

Zero

100

24. Absorption system normally uses the following refrigerant

Ammonia

Freon-11

Freon-22

CO2

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

Less

More/less depending on size of plant

Same

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

56 bars

Atmospheric pressure

24 bars

Slightly above atmospheric pressure

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

Low pressure side near receiver

Delivery of compressor

Suction of compressor

High pressure side close to receiver

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

Evaporator

Condenser

Compressor

Expansion valve

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

Decreases

Increases

Remain same

Depends on other factors

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. During dehumidification process, the relative humidity

Increases

Remains constant

Decreases

None of these

32. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

50 kcal/ min

33. 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

34. 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

35. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

Ammonia

R-12

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

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

37. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

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

Smelling

Using reagents

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

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

High pressure saturated liquid

Dry vapour

Very wet vapour

Wet vapour

40. 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 plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

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

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Refrigeration & Air-Conditioning Practice Set-1

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