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 reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

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

1.0

0.75

0.5

Zero

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

Humidification

Dehumidification

Cooling and dehumidification

Heating and humidification

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

Wet vapour

Superheated vapour

Dry saturated vapour

Saturated liquid

6. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

Equal to atmospheric pressure

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

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

8. During dehumidification process, the relative humidity

Increases

Remains constant

Decreases

None of these

9. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

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

100

20

Zero

50

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11. 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.

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

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

Suction of compressor

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

13. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

14. Absorption system normally uses the following refrigerant

CO2

Freon-22

Ammonia

Freon-11

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

Capillary tube

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

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

Sulphur sticks which on detection gives white smoke

Smelling

Halide torch which on detection produces greenish flame lighting

Using reagents

17. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

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

Expansion valve

Evaporator

Condenser

Compressor

19. 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

Humidity ratio

Relative humidity

Degree of saturation

Absolute humidity

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

Depends on other factors

Decreases

Increases

Remain same

Page 3 of 4

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

R-12

Ammonia

All of these

CO₂

22. During humidification process, __________ increases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

56 bars

24. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Decreases C.O.P

Other factors decide C.O.P

Increases C.O.P

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

Evaporator

Compressor

Condenser

Expansion valve

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

After passing through the expansion throttle valve

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

27. The moisture in a refrigerant is removed by

Driers

Evaporator

Dehumidifier

Safety relief valve

28. During humidification process, dry bulb temperature

None of these

Remains constant

Increases

Decreases

29. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Quiet operation

Cooling below 0°C

30. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

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

Orange

Yellow

Bright green

Red

32. 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

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

Wet vapour

Very wet vapour

Dry vapour

High pressure saturated liquid

34. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Water and hydrogen

Ammonia, water and hydrogen

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

Same

None of these

Lower

Higher

36. 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

Smaller cabinet should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

37. During sensible heating of air _________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

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

Less

Same

More

More/less depending on size of plant

39. 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

Wet bulb temperature

Dew point temperature

Dry bulb temperature

40. 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.

Refrigeration & Air-Conditioning Practice Set-1

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