Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

2. 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

3. During sensible heating of air _________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

4. 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

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

Suction of compressor

Low pressure side near receiver

Delivery of compressor

High pressure side close to receiver

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

Dry bulb temperature

None of these

Wet bulb temperature

Dew point temperature

7. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

8. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

R-12

Ammonia

Sulphur dioxide

9. During humidification process, dry bulb temperature

Decreases

Remains constant

Increases

None of these

10. Absorption system normally uses the following refrigerant

CO2

Freon-11

Ammonia

Freon-22

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11. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Very little power consumption

Noisy operation

12. The moisture in a refrigerant is removed by

Evaporator

Driers

Dehumidifier

Safety relief valve

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

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

14. 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

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

Evaporator

Condenser

Expansion valve

Compressor

16. 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.

17. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

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

Condenser

Evaporator

Compressor

Expansion valve

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

Zero

20

50

100

20. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Increases C.O.P

Other factors decide C.O.P

Page 3 of 4

21. During dehumidification process, the relative humidity

Increases

Remains constant

Decreases

None of these

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

Wet vapour

Saturated liquid

Dry saturated vapour

Superheated vapour

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

High pressure saturated liquid

Dry vapour

Very wet vapour

Wet vapour

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

Heating and humidification

Dehumidification

Humidification

Cooling and dehumidification

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

CO₂

Ammonia

All of these

R-12

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

Same

Higher

Lower

None of these

27. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

28. 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

Degree of saturation

Humidity ratio

Relative humidity

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

More

Less

Same

More/less depending on size of plant

30. 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

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

Bright green

Orange

Yellow

Red

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

May increase or decrease depending on the type of refrigerant used

Decrease

Remain unaffected

Increase

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

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Smelling

Using reagents

34. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

56 bars

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

36. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

37. 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

38. Which of the following statement is correct?

All of these

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.

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

Zero

0.75

1.0

0.5

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

Depends on other factors

Remain same

Decreases

Increases

Refrigeration & Air-Conditioning Practice Set-1

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