Refrigeration & Air-Conditioning Practice Set-1

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1. Pick up the incorrect statement

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

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

2. The moisture in a refrigerant is removed by

Evaporator

Safety relief valve

Dehumidifier

Driers

3. During humidification process, dry bulb temperature

None of these

Increases

Remains constant

Decreases

4. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

5. 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

Relative humidity

Absolute humidity

Humidity ratio

6. 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

7. 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

8. 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

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

Cooling and dehumidification

Humidification

Heating and humidification

Dehumidification

10. During dehumidification process, the relative humidity

Increases

Remains constant

Decreases

None of these

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11. During sensible heating of air _________ decreases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

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

Orange

Red

Yellow

Bright green

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

Depends on other factors

Decreases

Increases

Remain same

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

Same

More/less depending on size of plant

Less

More

15. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

Ammonia

CO2

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

Compressor

Expansion valve

Evaporator

Condenser

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

Thermostatic valve

Electrically operated throttling valve

Manually operated valve

Capillary tube

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

50

100

Zero

20

19. 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

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

Evaporator

Condenser

Compressor

Expansion valve

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21. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

22. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia and hydrogen

Ammonia, water and hydrogen

None of these

23. Under cooling in a refrigeration cycle

Increases C.O.P

C.O.P remains unaltered

Decreases C.O.P

Other factors decide C.O.P

24. 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

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

Lower

Same

None of these

Higher

26. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

27. 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

Increase

Remain unaffected

28. One ton refrigeration corresponds to

50 kcal/ min

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

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

Atmospheric pressure

Slightly above atmospheric pressure

56 bars

24 bars

30. Which of the following statement is wrong?

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.

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

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

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

32. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Very little power consumption

Quiet operation

33. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Sulphur dioxide

Carbon dioxide

34. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Wet vapour

Dry saturated vapour

Superheated vapour

Saturated liquid

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

0.5

Zero

0.75

1.0

37. Which of the following statement is correct?

All of these

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.

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

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

CO₂

Ammonia

All of these

R-12

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

Before entering the expansion valve

Before passing through the condenser

After passing through the expansion throttle valve

After passing through the condenser

40. 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

Refrigeration & Air-Conditioning Practice Set-1

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