Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Dry saturated vapour

Superheated vapour

Saturated liquid

Wet vapour

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

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

Remain unaffected

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

Using reagents

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Smelling

4. An important characteristic of absorption system of refrigeration is

Noisy operation

Very little power consumption

Cooling below 0°C

Quiet operation

5. Pick up the incorrect statement

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

Lithium bromide used in vapour absorption cycle is non volatile

6. 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.

7. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

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

Condenser

Expansion valve

Evaporator

Compressor

9. 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

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

Manually operated valve

Electrically operated throttling valve

Thermostatic valve

Capillary tube

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

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

12. Absorption system normally uses the following refrigerant

Freon-11

Ammonia

CO2

Freon-22

13. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

14. 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

15. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Increases C.O.P

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

CO₂

All of these

R-12

Ammonia

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

Yellow

Red

Bright green

Orange

18. During humidification process, __________ increases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

19. During humidification process, dry bulb temperature

Decreases

Increases

None of these

Remains constant

20. During dehumidification process, the relative humidity

Increases

None of these

Remains constant

Decreases

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

Atmospheric pressure

56 bars

24 bars

Slightly above atmospheric pressure

22. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

Perfectly tight vapour seal should be used

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

Evaporator

Expansion valve

Condenser

Compressor

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

Dehumidification

Cooling and dehumidification

Humidification

Heating and humidification

25. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

26. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Ammonia

Carbon dioxide

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

Increases

Depends on other factors

Remain same

Decreases

28. 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

29. 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

None of these

Wet bulb temperature

Dry bulb temperature

30. 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

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31. 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.

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

More/less depending on size of plant

Less

Same

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

Zero

100

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

0.75

0.5

Zero

1.0

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

High pressure side close to receiver

Low pressure side near receiver

Delivery of compressor

Suction of compressor

36. 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

Humidity ratio

Absolute humidity

37. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Safety relief valve

Driers

38. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

39. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

None of these

40. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

Refrigeration & Air-Conditioning Practice Set-1

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