Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

Red

Bright green

Orange

Yellow

2. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

3. An important characteristic of absorption system of refrigeration is

Very little power consumption

Cooling below 0°C

Noisy operation

Quiet operation

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

Evaporator

Condenser

Compressor

Expansion valve

5. 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.

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.

All of these

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

Manually operated valve

Electrically operated throttling valve

Thermostatic valve

Capillary tube

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

Decreases

Remain same

Increases

Depends on other factors

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

Humidification

Cooling and dehumidification

Dehumidification

Heating and humidification

9. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

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

Superheated vapour

Wet vapour

Dry saturated vapour

Saturated liquid

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

Less

Same

More/less depending on size of plant

More

12. 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

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

13. 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

Absolute humidity

Degree of saturation

14. Absorption system normally uses the following refrigerant

CO2

Freon-22

Ammonia

Freon-11

15. Which of the following statement is wrong?

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

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.

In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

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

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Decrease

17. 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

18. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Evaporator

Safety relief valve

19. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

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

Wet bulb temperature

Dry bulb temperature

Dew point temperature

None of these

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

None of these

Lower

Same

Higher

22. 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

23. During humidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

24. Pick up the incorrect statement

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

Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

25. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Water and hydrogen

None of these

Ammonia and hydrogen

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

CO₂

All of these

R-12

Ammonia

27. During dehumidification process, the relative humidity

None of these

Increases

Decreases

Remains constant

28. One ton refrigeration corresponds to

50 kcal/ min

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

29. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

30. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

High pressure side close to receiver

Suction of compressor

Delivery of compressor

Low pressure side near receiver

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

50

20

Zero

100

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

0.75

Zero

0.5

1.0

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

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

35. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

36. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

37. 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

38. 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

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

Condenser

Expansion valve

Compressor

Evaporator

40. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Refrigeration & Air-Conditioning Practice Set-1

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