Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

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

Manually operated valve

Thermostatic valve

Electrically operated throttling valve

Capillary tube

2. During sensible heating of air _________ decreases.

Relative humidity

Dry bulb temperature

Specific humidity

Wet bulb temperature

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

Orange

Yellow

Bright green

Red

4. During humidification process, dry bulb temperature

Decreases

Increases

None of these

Remains constant

5. Under cooling in a refrigeration cycle

Increases C.O.P

C.O.P remains unaltered

Decreases C.O.P

Other factors decide C.O.P

6. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

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

Zero

0.5

1.0

0.75

8. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

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. 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.

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

56 bars

24 bars

Atmospheric pressure

Slightly above atmospheric pressure

12. 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

Dry bulb temperature

Wet bulb temperature

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

Decreases

Remain same

Depends on other factors

Increases

14. 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

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

Zero

100

16. Pick up the incorrect statement

A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

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

Lithium bromide used in vapour absorption cycle is non volatile

17. During humidification process, __________ increases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

18. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

19. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

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

Ammonia

All of these

R-12

CO₂

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

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

22. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

23. 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.

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

All of these

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

24. During dehumidification process, the relative humidity

None of these

Increases

Remains constant

Decreases

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

None of these

Same

Lower

Higher

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

After passing through the condenser

Before passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

27. 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

Humidity ratio

Absolute humidity

Relative humidity

Degree of saturation

28. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

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

Dry vapour

Very wet vapour

High pressure saturated liquid

Wet vapour

30. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Very little power consumption

Noisy operation

Quiet operation

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31. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

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

Cooling and dehumidification

Dehumidification

Humidification

Heating and humidification

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

Evaporator

Compressor

Expansion valve

Condenser

34. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Safety relief valve

Evaporator

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

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

36. Absorption system normally uses the following refrigerant

Freon-22

CO2

Ammonia

Freon-11

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

Decrease

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

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

Condenser

Compressor

Expansion valve

Evaporator

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

Dry saturated vapour

Wet vapour

Superheated vapour

Saturated liquid

40. 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

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Refrigeration & Air-Conditioning Practice Set-1

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