Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

Very wet vapour

High pressure saturated liquid

Dry vapour

Wet vapour

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

Expansion valve

Compressor

Evaporator

Condenser

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

Red

Bright green

Orange

Yellow

4. Absorption system normally uses the following refrigerant

Freon-11

CO2

Freon-22

Ammonia

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

Zero

100

20

50

6. During humidification process, dry bulb temperature

Increases

Decreases

Remains constant

None of these

7. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

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

Dry saturated vapour

Wet vapour

Superheated vapour

Saturated liquid

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

Capillary tube

Manually operated valve

Thermostatic valve

Electrically operated throttling valve

10. During humidification process, __________ increases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

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

Humidification

Cooling and dehumidification

Dehumidification

Heating and humidification

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

R-12

CO₂

Ammonia

All of these

13. One ton refrigeration corresponds to

50 kcal/ hr

50 kcal/ min

80 kcal/ min

80 kcal/ hr

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

15. Which of the following statement is wrong?

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

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.

16. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

17. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

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

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

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

Delivery of compressor

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

20. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Very little power consumption

Noisy operation

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21. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Driers

Evaporator

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

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

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

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

24. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

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

Absolute humidity

Degree of saturation

Relative humidity

Humidity ratio

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

24 bars

56 bars

Atmospheric pressure

Slightly above atmospheric pressure

27. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

28. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

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

None of these

Same

Lower

Higher

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

Condenser

Compressor

Evaporator

Expansion valve

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31. Which of the following statement is correct?

All of these

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

Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.

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

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

0.5

1.0

Zero

0.75

33. Under cooling in a refrigeration cycle

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Decreases C.O.P

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

More/less depending on size of plant

Less

More

Same

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

Depends on other factors

Decreases

Increases

Remain same

36. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

37. 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

Dew point temperature

Wet bulb temperature

38. 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

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

39. Pick up the incorrect statement

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

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

Lithium bromide plant can't operate below 0°C

40. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

Refrigeration & Air-Conditioning Practice Set-1

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