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

Superheated vapour

Dry saturated vapour

Saturated liquid

Wet vapour

2. 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

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

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

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

56 bars

Slightly above atmospheric pressure

24 bars

Atmospheric pressure

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

Expansion valve

Evaporator

Condenser

Compressor

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

Zero

100

7. 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

8. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

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

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

More/less depending on size of plant

Less

Same

10. 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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

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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

Degree of saturation

Humidity ratio

Relative humidity

Absolute humidity

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

Dry vapour

Wet vapour

High pressure saturated liquid

Very wet vapour

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

Remain same

Decreases

Increases

Depends on other factors

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

After passing through the expansion throttle valve

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

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

Low pressure side near receiver

Delivery of compressor

Suction of compressor

High pressure side close to receiver

16. During sensible heating of air _________ decreases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

17. 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

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

Condenser

Evaporator

Compressor

Expansion valve

19. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

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

Humidification

Heating and humidification

Cooling and dehumidification

Dehumidification

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21. 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

22. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

50 kcal/ min

23. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

24. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

25. During sensible cooling of air ________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

26. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

27. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia and hydrogen

Ammonia, water and hydrogen

28. 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

29. During humidification process, dry bulb temperature

None of these

Increases

Remains constant

Decreases

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

0.75

0.5

1.0

Zero

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31. 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 high condensing pressures

Large displacements and low condensing pressures

32. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Lower than atmospheric pressure

Could be anything

33. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

Ammonia

R-12

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

R-12

Ammonia

All of these

CO₂

35. Which of the following statement is wrong?

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.

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

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

Capillary tube

37. During dehumidification process, the relative humidity

None of these

Remains constant

Decreases

Increases

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

Red

Bright green

Yellow

Orange

39. An important characteristic of absorption system of refrigeration is

Noisy operation

Quiet operation

Cooling below 0°C

Very little power consumption

40. Which of the following statement is correct?

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

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

In vapour absorption refrigerator, the compression of refrigerant is avoided.

All of these

Refrigeration & Air-Conditioning Practice Set-1

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