Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

2. 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

3. During humidification process, __________ increases.

Relative humidity

Dry bulb temperature

Specific humidity

Wet bulb temperature

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

Evaporator

Expansion valve

Condenser

Compressor

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

Zero

100

6. 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

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

8. 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

Remain unaffected

Increase

9. 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

Absolute humidity

Humidity ratio

Relative humidity

10. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Ammonia, water and hydrogen

None of these

Water and hydrogen

Page 2 of 4

11. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Cooling below 0°C

Noisy operation

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

None of these

Lower

Higher

Same

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

Yellow

Bright green

Orange

Red

14. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

15. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

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

Delivery of compressor

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

17. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

18. During humidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

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

Slightly above atmospheric pressure

56 bars

24 bars

Atmospheric pressure

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

Zero

0.75

1.0

0.5

Page 3 of 4

21. 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

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

Evaporator

Condenser

Compressor

Expansion valve

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

Less

More/less depending on size of plant

Same

24. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-22

Freon-11

25. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

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

Before passing through the condenser

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

27. Which of the following statement is correct?

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

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

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.

28. 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

None of these

Dry bulb temperature

Dew point temperature

29. Which of the following statement is wrong?

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.

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.

30. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Safety relief valve

Driers

Page 4 of 4

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

Increases

Remain same

Depends on other factors

Decreases

32. 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

33. During sensible cooling of air ________ decreases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

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

R-12

CO₂

All of these

Ammonia

35. Pick up the incorrect statement

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

Lithium bromide plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

36. Under cooling in a refrigeration cycle

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

37. During sensible heating of air _________ decreases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

38. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ min

80 kcal/ hr

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

Saturated liquid

Wet vapour

Superheated vapour

Dry saturated vapour

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

Heating and humidification

Dehumidification

Cooling and dehumidification

Humidification

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Refrigeration & Air-Conditioning Practice Set-1

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