Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. 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

Absolute humidity

Humidity ratio

Degree of saturation

Relative humidity

2. The moisture in a refrigerant is removed by

Evaporator

Safety relief valve

Dehumidifier

Driers

3. During sensible heating of air _________ decreases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

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

Expansion valve

Condenser

Compressor

Evaporator

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

Suction of compressor

High pressure side close to receiver

Low pressure side near receiver

Delivery of compressor

6. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

7. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Ammonia

Carbon dioxide

8. 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.

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

More

More/less depending on size of plant

Less

Same

10. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

Page 2 of 4

11. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

12. 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

13. During humidification process, dry bulb temperature

Decreases

Remains constant

Increases

None of these

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

Orange

Bright green

Yellow

Red

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

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

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

Higher

Same

Lower

None of these

17. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ min

50 kcal/ min

80 kcal/ hr

18. 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

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

19. 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

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

Manually operated valve

Electrically operated throttling valve

Capillary tube

Thermostatic valve

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21. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

22. 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

23. 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

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

Remain same

Increases

Depends on other factors

Decreases

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

20

Zero

50

100

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

Cooling and dehumidification

Heating and humidification

Humidification

Dehumidification

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

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

28. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

29. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

30. Which of the following statement is wrong?

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.

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

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31. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

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

1.0

0.75

Zero

0.5

33. Pick up the incorrect statement

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

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

34. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Noisy operation

Very little power consumption

Quiet operation

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

After passing through the expansion throttle valve

Before passing through the condenser

After passing through the condenser

Before entering the expansion valve

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

Expansion valve

Compressor

Condenser

Evaporator

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

Ammonia

CO₂

All of these

R-12

38. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

Equal to atmospheric pressure

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

40. During dehumidification process, the relative humidity

Remains constant

None of these

Increases

Decreases

Refrigeration & Air-Conditioning Practice Set-1

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