Refrigeration & Air-Conditioning Practice Set-1

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1. Which of the following statement is correct?

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.

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

All of these

2. 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

Relative humidity

Degree of saturation

Absolute humidity

Humidity ratio

3. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

4. 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

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

Heating and humidification

Dehumidification

Humidification

Cooling and dehumidification

6. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Cooling below 0°C

Quiet operation

7. Absorption system normally uses the following refrigerant

Freon-11

CO2

Freon-22

Ammonia

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

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

9. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

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

Capillary tube

Thermostatic valve

Manually operated valve

Electrically operated throttling valve

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11. 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

Dew point temperature

Dry bulb temperature

None of these

12. 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

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

Wet vapour

High pressure saturated liquid

Very wet vapour

Dry vapour

14. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

80 kcal/ min

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

Bright green

Yellow

Orange

Red

16. The moisture in a refrigerant is removed by

Dehumidifier

Driers

Safety relief valve

Evaporator

17. During humidification process, dry bulb temperature

Remains constant

None of these

Increases

Decreases

18. Pick up the incorrect statement

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

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

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

Superheated vapour

Dry saturated vapour

Wet vapour

Saturated liquid

20. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

R-12

Ammonia

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

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

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

100

Zero

20

50

23. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

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

More

Same

Less

More/less depending on size of plant

25. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

26. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

27. 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

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

Condenser

Compressor

Evaporator

Expansion valve

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

Zero

1.0

0.5

0.75

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

R-12

All of these

CO₂

Ammonia

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31. During dehumidification process, the relative humidity

Increases

Remains constant

None of these

Decreases

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

Suction of compressor

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

33. 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

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

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

After passing through the expansion throttle valve

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

Compressor

Condenser

Expansion valve

Evaporator

36. 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.

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

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

37. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

38. During humidification process, __________ increases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

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

Remain unaffected

Decrease

May increase or decrease depending on the type of refrigerant used

Increase

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

Depends on other factors

Increases

Decreases

Remain same

Refrigeration & Air-Conditioning Practice Set-1

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