Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

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

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

2. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Water and hydrogen

None of these

Ammonia, water and hydrogen

3. During humidification process, dry bulb temperature

Remains constant

Decreases

None of these

Increases

4. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Driers

Safety relief valve

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

Zero

20

100

50

6. 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

7. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

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

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

Remain unaffected

9. During dehumidification process, the relative humidity

Remains constant

Decreases

None of these

Increases

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

Decreases

Remain same

Increases

Depends on other factors

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

Dry vapour

Wet vapour

Very wet vapour

High pressure saturated liquid

12. 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

13. During sensible heating of air _________ decreases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

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

Condenser

Evaporator

Expansion valve

Compressor

15. Which of the following statement is correct?

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

All of these

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

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

16. 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

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

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

24 bars

56 bars

Slightly above atmospheric pressure

Atmospheric pressure

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

Red

Yellow

Orange

Bright green

19. Absorption system normally uses the following refrigerant

Freon-11

CO2

Ammonia

Freon-22

20. 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

Absolute humidity

Humidity ratio

Degree of saturation

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

Wet vapour

Saturated liquid

Superheated vapour

Dry saturated vapour

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

Before passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

After passing through the condenser

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

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

Capillary tube

24. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

25. 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

Dry bulb temperature

Dew point temperature

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

0.75

0.5

1.0

Zero

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

Heating and humidification

Dehumidification

Humidification

Cooling and dehumidification

28. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

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

Using reagents

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Smelling

30. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

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

Evaporator

Compressor

Condenser

Expansion valve

32. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

33. An important characteristic of absorption system of refrigeration is

Very little power consumption

Cooling below 0°C

Quiet operation

Noisy operation

34. Under cooling in a refrigeration cycle

Other factors decide C.O.P

C.O.P remains unaltered

Decreases C.O.P

Increases C.O.P

35. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

Higher than atmospheric pressure

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

All of these

R-12

Ammonia

CO₂

37. During sensible cooling of air ________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

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

More/less depending on size of plant

Less

More

Same

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

None of these

Same

Higher

Lower

40. 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.

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.

Refrigeration & Air-Conditioning Practice Set-1

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