Refrigeration & Air-Conditioning Practice Set-1

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1. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

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

Cooling and dehumidification

Humidification

Heating and humidification

Dehumidification

3. Under cooling in a refrigeration cycle

Increases C.O.P

Other factors decide C.O.P

Decreases C.O.P

C.O.P remains unaltered

4. An important characteristic of absorption system of refrigeration is

Noisy operation

Quiet operation

Very little power consumption

Cooling below 0°C

5. Which of the following statement is correct?

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.

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.

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

Bright green

Orange

Yellow

Red

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

Before passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

After passing through the condenser

8. During dehumidification process, the relative humidity

Remains constant

Increases

None of these

Decreases

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

Very wet vapour

Wet vapour

High pressure saturated liquid

Dry vapour

10. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

None of these

Water and hydrogen

Ammonia and hydrogen

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11. 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

Humidity ratio

Relative humidity

12. 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

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

13. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Evaporator

Driers

14. During humidification process, __________ increases.

Relative humidity

Dry bulb temperature

Specific humidity

Wet bulb temperature

15. Which of the following statement is wrong?

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

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

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

CO₂

All of these

R-12

Ammonia

17. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

18. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Ammonia

Sulphur dioxide

19. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

80 kcal/ min

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

Thermostatic valve

Electrically operated throttling valve

Capillary tube

Manually operated valve

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

20

Zero

50

100

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

Condenser

Expansion valve

Compressor

Evaporator

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

Lower

Higher

Same

None of these

24. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

26. Pick up the incorrect statement

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

Lithium bromide plant can't operate below 0°C

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

Slightly above atmospheric pressure

56 bars

Atmospheric pressure

24 bars

28. 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

Remain unaffected

Increase

29. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

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

Decreases

Depends on other factors

Increases

Remain same

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

More

Less

Same

More/less depending on size of plant

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

Saturated liquid

Wet vapour

Superheated vapour

Dry saturated vapour

33. 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

None of these

Dry bulb temperature

34. During sensible heating of air _________ decreases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

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

Zero

1.0

0.75

0.5

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

Expansion valve

Condenser

Compressor

Evaporator

37. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

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

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Suction of compressor

39. During humidification process, dry bulb temperature

None of these

Remains constant

Increases

Decreases

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

Smelling

Using reagents

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Refrigeration & Air-Conditioning Practice Set-1

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