Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. Pick up the incorrect statement

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

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

2. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Driers

Dehumidifier

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

Smelling

Using reagents

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

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

20

Zero

50

100

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

Atmospheric pressure

24 bars

Slightly above atmospheric pressure

56 bars

6. 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

7. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

8. During sensible cooling of air ________ decreases.

Dry bulb temperature

Specific humidity

Wet bulb temperature

Relative humidity

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

High pressure saturated liquid

Very wet vapour

Dry vapour

Wet vapour

10. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ min

80 kcal/ hr

50 kcal/ hr

Page 2 of 4

11. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

None of these

Ammonia and hydrogen

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

More/less depending on size of plant

Less

More

Same

13. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

14. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Sulphur dioxide

Carbon dioxide

15. 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

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

Capillary tube

Thermostatic valve

Manually operated valve

Electrically operated throttling valve

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

Higher

Lower

Same

None of these

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

Before passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

After passing through the condenser

19. 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

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

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

Expansion valve

Compressor

Evaporator

Condenser

Page 3 of 4

21. 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

Dew point temperature

Wet bulb temperature

Dry bulb temperature

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

Saturated liquid

Dry saturated vapour

Wet vapour

Superheated vapour

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

0.75

0.5

Zero

1.0

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

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

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

R-12

CO₂

All of these

Ammonia

26. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

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

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Decrease

28. Under cooling in a refrigeration cycle

Increases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Decreases C.O.P

29. During humidification process, dry bulb temperature

None of these

Remains constant

Decreases

Increases

30. Which of the following statement is wrong?

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.

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

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

Page 4 of 4

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

Decreases

Depends on other factors

Remain same

Increases

32. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

33. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

34. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Noisy operation

Cooling below 0°C

35. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

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

Expansion valve

Compressor

Condenser

Evaporator

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

Bright green

Yellow

Orange

Red

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

Cooling and dehumidification

Dehumidification

Humidification

Heating and humidification

39. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-22

Freon-11

40. Which of the following statement is correct?

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

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

Refrigeration & Air-Conditioning Practice Set-1

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