Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. Pick up the incorrect statement

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

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

2. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

3. 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

4. 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

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

Orange

Yellow

Bright green

Red

6. During humidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

7. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Increases C.O.P

Other factors decide C.O.P

Decreases C.O.P

8. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

9. During dehumidification process, the relative humidity

Increases

Decreases

Remains constant

None of these

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

1.0

0.75

Zero

0.5

Page 2 of 4

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

Compressor

Evaporator

Condenser

Expansion valve

12. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Lower than atmospheric pressure

Higher than atmospheric pressure

Could be anything

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

All of these

R-12

Ammonia

CO₂

14. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called

Dew point temperature

Dry bulb temperature

Wet bulb temperature

None of these

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

After passing through the expansion throttle valve

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

16. Absorption system normally uses the following refrigerant

Freon-11

Ammonia

Freon-22

CO2

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

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

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

24 bars

Atmospheric pressure

56 bars

Slightly above atmospheric pressure

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

Zero

100

20. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

Page 3 of 4

21. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Cooling below 0°C

Quiet operation

22. The moisture in a refrigerant is removed by

Dehumidifier

Driers

Evaporator

Safety relief valve

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

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

24. 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

25. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

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

Dehumidification

Heating and humidification

Humidification

Cooling and dehumidification

27. 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

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

Smaller cabinet should be used

28. Which of the following statement is correct?

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

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

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

29. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

80 kcal/ min

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

Delivery of compressor

Suction of compressor

Low pressure side near receiver

High pressure side close to receiver

Page 4 of 4

31. Which of the following statement is wrong?

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

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

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.

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

Evaporator

Condenser

Expansion valve

Compressor

33. During sensible cooling of air ________ decreases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

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

More/less depending on size of plant

Less

Same

35. 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

Dry vapour

Wet vapour

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

Superheated vapour

Saturated liquid

Wet vapour

Dry saturated vapour

37. The fluids used in Electrolux refrigerator are

None of these

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

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

Depends on other factors

Decreases

Increases

Remain same

39. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

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

None of these

Lower

Same

Higher

Refrigeration & Air-Conditioning Practice Set-1

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