Refrigeration & Air-Conditioning Practice Set-1

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

Compressor

Condenser

Expansion valve

Evaporator

2. 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 condenser

After passing through the expansion throttle valve

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

Superheated vapour

Dry saturated vapour

Wet vapour

Saturated liquid

4. During humidification process, __________ increases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

5. During humidification process, dry bulb temperature

Decreases

None of these

Increases

Remains constant

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

20

50

100

Zero

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

All of these

CO₂

R-12

Ammonia

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

Electrically operated throttling valve

Manually operated valve

Capillary tube

Thermostatic valve

9. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia and hydrogen

None of these

Ammonia, water and hydrogen

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

Heating and humidification

Humidification

Cooling and dehumidification

Dehumidification

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11. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

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

Very wet vapour

Wet vapour

Dry vapour

High pressure saturated liquid

13. The moisture in a refrigerant is removed by

Evaporator

Driers

Safety relief valve

Dehumidifier

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

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

15. 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

16. Absorption system normally uses the following refrigerant

Freon-22

CO2

Ammonia

Freon-11

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

Remain unaffected

Increase

Decrease

May increase or decrease depending on the type of refrigerant used

18. 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

Perfectly tight vapour seal should be used

Smaller cabinet should be used

Bigger cabinet should be used

19. Chaperon equation is a relation between

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

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

Remain same

Decreases

Depends on other factors

Increases

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

Red

Yellow

Orange

Bright green

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

0.75

1.0

0.5

Zero

23. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

24. Which of the following statement is correct?

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

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.

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

Halide torch which on detection produces greenish flame lighting

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

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

Evaporator

Condenser

Compressor

Expansion valve

27. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ min

80 kcal/ min

50 kcal/ hr

28. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

29. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Noisy operation

Cooling below 0°C

30. 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

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31. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Ammonia

Carbon dioxide

32. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

33. During sensible cooling of air ________ decreases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

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

More

Same

Less

More/less depending on size of plant

35. Which of the following statement is wrong?

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

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

36. During dehumidification process, the relative humidity

None of these

Decreases

Increases

Remains constant

37. 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

Dry bulb temperature

None of these

38. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

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

39. 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

Absolute humidity

Humidity ratio

Degree of saturation

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

Slightly above atmospheric pressure

24 bars

56 bars

Atmospheric pressure

Refrigeration & Air-Conditioning Practice Set-1

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