Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. During humidification process, __________ increases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

2. 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

Increase

Remain unaffected

3. 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.

4. Absorption system normally uses the following refrigerant

Freon-11

Freon-22

Ammonia

CO2

5. Which of the following statement is correct?

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.

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.

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

56 bars

24 bars

Slightly above atmospheric pressure

Atmospheric pressure

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

0.5

0.75

1.0

Zero

8. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

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

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

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

Halide torch which on detection produces greenish flame lighting

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

10. 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

Page 2 of 4

11. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

12. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Noisy operation

Very little power consumption

13. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

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

R-12

CO₂

Ammonia

All of these

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

High pressure side close to receiver

Delivery of compressor

Low pressure side near receiver

Suction of compressor

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

Zero

100

17. 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

Dew point temperature

Wet bulb temperature

None of these

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

Condenser

Evaporator

Compressor

Expansion valve

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

Higher

None of these

Lower

Same

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

Compressor

Evaporator

Expansion valve

Condenser

Page 3 of 4

21. During sensible cooling of air ________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

22. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

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

Orange

Red

Bright green

Yellow

24. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Increases C.O.P

Other factors decide C.O.P

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

Dry saturated vapour

Wet vapour

Saturated liquid

Superheated vapour

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

Thermostatic valve

Capillary tube

Electrically operated throttling valve

Manually operated valve

27. During humidification process, dry bulb temperature

Remains constant

Decreases

Increases

None of these

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

More/less depending on size of plant

Less

Same

29. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

50 kcal/ min

30. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Water and hydrogen

Ammonia, water and hydrogen

None of these

Page 4 of 4

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

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

32. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Safety relief valve

Driers

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

Dry vapour

High pressure saturated liquid

Wet vapour

Very wet vapour

34. The refrigerant widely used in domestic refrigerators is

Ammonia

Sulphur dioxide

R-12

Carbon dioxide

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

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

After passing through the expansion throttle valve

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

Humidification

Cooling and dehumidification

Dehumidification

Heating and humidification

37. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

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

Depends on other factors

Remain same

Increases

Decreases

39. During sensible heating of air _________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

40. 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

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Refrigeration & Air-Conditioning Practice Set-1

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