Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

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

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

After passing through the expansion throttle valve

3. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

4. 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

5. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Noisy operation

Very little power consumption

6. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

50 kcal/ min

7. 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

Degree of saturation

Humidity ratio

Relative humidity

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

Delivery of compressor

Suction of compressor

High pressure side close to receiver

Low pressure side near receiver

9. 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

Dew point temperature

Dry bulb temperature

None of these

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

1.0

0.75

Zero

0.5

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11. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

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

High pressure saturated liquid

Wet vapour

Very wet vapour

Dry vapour

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

More/less depending on size of plant

Same

Less

14. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Safety relief valve

Evaporator

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

Evaporator

Condenser

Expansion valve

Compressor

16. During dehumidification process, the relative humidity

None of these

Remains constant

Decreases

Increases

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

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

Halide torch which on detection produces greenish flame lighting

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

Cooling and dehumidification

Heating and humidification

Dehumidification

Humidification

19. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

20. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

Page 3 of 4

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

Increases

Remain same

Decreases

Depends on other factors

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

56 bars

Slightly above atmospheric pressure

Atmospheric pressure

24 bars

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

Saturated liquid

Wet vapour

Dry saturated vapour

Superheated vapour

24. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

25. Absorption system normally uses the following refrigerant

Freon-22

Ammonia

Freon-11

CO2

26. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

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

All of these

Ammonia

CO₂

R-12

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

Red

Bright green

Yellow

Orange

30. Which of the following statement is wrong?

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

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.

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

Page 4 of 4

31. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

32. During humidification process, dry bulb temperature

Decreases

Increases

Remains constant

None of these

33. 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

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

Condenser

Expansion valve

Compressor

Evaporator

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

Zero

100

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

Remain unaffected

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

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

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

38. Which of the following statement is correct?

All of these

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.

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

39. 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

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

Lower

None of these

Higher

Same

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Refrigeration & Air-Conditioning Practice Set-1

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