Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

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

None of these

Higher

Same

Lower

2. 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

Dry bulb temperature

Wet bulb temperature

Dew point temperature

3. The refrigerant widely used in domestic refrigerators is

Ammonia

Carbon dioxide

Sulphur dioxide

R-12

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

Increases

Depends on other factors

Remain same

Decreases

5. During sensible heating of air _________ decreases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

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

0.5

Zero

0.75

1.0

7. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

80 kcal/ min

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

Orange

Red

Bright green

Yellow

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

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

10. 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

Page 2 of 4

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

All of these

R-12

CO₂

Ammonia

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

Zero

100

13. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

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

Dry saturated vapour

Superheated vapour

Saturated liquid

Wet vapour

15. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Noisy operation

Cooling below 0°C

16. Pick up the incorrect statement

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

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

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

Condenser

Evaporator

Compressor

Expansion valve

18. 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

19. Which of the following statement is correct?

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

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

All of these

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

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

High pressure saturated liquid

Wet vapour

Dry vapour

Very wet vapour

Page 3 of 4

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

Same

Less

More/less depending on size of plant

22. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Water and hydrogen

None of these

Ammonia, water and hydrogen

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

Increase

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

24. The moisture in a refrigerant is removed by

Evaporator

Driers

Dehumidifier

Safety relief valve

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

Cooling and dehumidification

Heating and humidification

Humidification

Dehumidification

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

Compressor

Condenser

Evaporator

Expansion valve

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

Suction of compressor

Delivery of compressor

Low pressure side near receiver

High pressure side close to receiver

28. Which of the following statement is wrong?

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.

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.

29. 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

30. During humidification process, dry bulb temperature

Decreases

Remains constant

Increases

None of these

Page 4 of 4

31. Absorption system normally uses the following refrigerant

Ammonia

Freon-22

CO2

Freon-11

32. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

33. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

34. During dehumidification process, the relative humidity

None of these

Decreases

Remains constant

Increases

35. 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

36. 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

37. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

38. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

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

Thermostatic valve

Electrically operated throttling valve

Capillary tube

Manually operated valve

40. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Refrigeration & Air-Conditioning Practice Set-1

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