Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Cooling below 0°C

Quiet operation

2. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

3. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

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

Halide torch which on detection produces greenish flame lighting

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

5. Pick up the incorrect statement

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

Lithium bromide plant can't operate below 0°C

6. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Decreases C.O.P

C.O.P remains unaltered

Increases C.O.P

7. 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

Wet bulb temperature

None of these

Dry bulb temperature

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

After passing through the expansion throttle valve

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

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

Thermostatic valve

Manually operated valve

Electrically operated throttling valve

Capillary tube

10. 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

Absolute humidity

Degree of saturation

Relative humidity

Page 2 of 4

11. During sensible cooling of air ________ decreases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

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

Compressor

Evaporator

Expansion valve

Condenser

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

Depends on other factors

Decreases

Increases

Remain same

14. 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

15. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Smaller cabinet should be used

16. During sensible heating of air _________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

17. During dehumidification process, the relative humidity

Decreases

Remains constant

None of these

Increases

18. 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

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

High pressure saturated liquid

Dry vapour

Wet vapour

Very wet vapour

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

Decrease

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

Page 3 of 4

21. During humidification process, dry bulb temperature

Increases

Remains constant

Decreases

None of these

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

20

50

100

Zero

23. 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

24. 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

25. Which of the following statement is wrong?

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.

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.

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

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

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

Condenser

Compressor

Expansion valve

Evaporator

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

1.0

Zero

0.75

0.5

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

Orange

Bright green

Red

Yellow

30. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

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

CO₂

R-12

Ammonia

All of these

32. One ton refrigeration corresponds to

50 kcal/ hr

50 kcal/ min

80 kcal/ min

80 kcal/ hr

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

Wet vapour

Dry saturated vapour

Saturated liquid

Superheated vapour

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

Same

Less

More

More/less depending on size of plant

35. The refrigerant widely used in domestic refrigerators is

R-12

Sulphur dioxide

Ammonia

Carbon dioxide

36. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

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

Dehumidification

Humidification

Heating and humidification

Cooling and dehumidification

38. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Driers

Safety relief valve

39. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

40. Which of the following statement is correct?

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

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.

Refrigeration & Air-Conditioning Practice Set-1

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