Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

After passing through the expansion throttle valve

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

2. During humidification process, dry bulb temperature

None of these

Remains constant

Increases

Decreases

3. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

4. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Equal to atmospheric pressure

Lower than atmospheric pressure

5. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

6. 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

Dew point temperature

Dry bulb temperature

7. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Driers

Dehumidifier

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

Thermostatic valve

Manually operated valve

Capillary tube

Electrically operated throttling valve

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

Bigger cabinet should be used

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

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

Superheated vapour

Saturated liquid

Wet vapour

Dry saturated vapour

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11. During sensible cooling of air ________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

12. Which of the following statement is wrong?

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 vapour compression cycle, the useful part of the heat transfer is at the condenser.

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

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

Slightly above atmospheric pressure

24 bars

Atmospheric pressure

56 bars

14. During sensible heating of air _________ decreases.

Relative humidity

Dry bulb temperature

Specific humidity

Wet bulb temperature

15. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia, water and hydrogen

Ammonia and hydrogen

16. 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

17. An important characteristic of absorption system of refrigeration is

Very little power consumption

Quiet operation

Noisy operation

Cooling below 0°C

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

Low pressure side near receiver

High pressure side close to receiver

Suction of compressor

Delivery of compressor

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

Expansion valve

Evaporator

Compressor

Condenser

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

Bright green

Red

Yellow

Orange

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21. Under cooling in a refrigeration cycle

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

22. During dehumidification process, the relative humidity

Remains constant

Increases

None of these

Decreases

23. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

24. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

25. 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

Degree of saturation

Humidity ratio

Relative humidity

Absolute humidity

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

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

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

Lower

Higher

None of these

Same

28. Absorption system normally uses the following refrigerant

Freon-11

Ammonia

Freon-22

CO2

29. 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

30. Which of the following statement is correct?

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

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

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

CO₂

All of these

R-12

Ammonia

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

Cooling and dehumidification

Dehumidification

Humidification

Heating and humidification

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

Compressor

Expansion valve

Condenser

Evaporator

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

Remain same

Depends on other factors

Decreases

Increases

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

Dry vapour

High pressure saturated liquid

Wet vapour

Very wet vapour

36. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

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

More/less depending on size of plant

Same

Less

More

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

Zero

1.0

0.5

0.75

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

Zero

50

100

20

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

Using reagents

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Smelling

Refrigeration & Air-Conditioning Practice Set-1

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