Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

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

0.5

0.75

Zero

1.0

2. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

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

R-12

CO₂

All of these

Ammonia

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

Before entering the expansion valve

After passing through the expansion throttle valve

Before passing through the condenser

After passing through the condenser

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

Very wet vapour

High pressure saturated liquid

Wet vapour

Dry vapour

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

Zero

100

7. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

Increases C.O.P

C.O.P remains unaltered

8. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Equal to atmospheric pressure

Lower than atmospheric pressure

9. Which of the following statement is wrong?

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.

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.

10. Absorption system normally uses the following refrigerant

CO2

Ammonia

Freon-11

Freon-22

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

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

Halide torch which on detection produces greenish flame lighting

12. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

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

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

Depends on other factors

Decreases

Increases

Remain same

14. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

80 kcal/ min

15. 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

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

Expansion valve

Condenser

Evaporator

Compressor

17. 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

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

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

Delivery of compressor

19. 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 two heat exchangers

Two cooling turbines and one heat exchanger

20. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Safety relief valve

Evaporator

Page 3 of 4

21. During humidification process, dry bulb temperature

None of these

Increases

Decreases

Remains constant

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

More/less depending on size of plant

Same

Less

23. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called

None of these

Wet bulb temperature

Dry bulb temperature

Dew point temperature

24. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

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

Yellow

Bright green

Orange

Red

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

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

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

Saturated liquid

Wet vapour

Dry saturated vapour

Superheated vapour

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

Evaporator

Expansion valve

Compressor

Condenser

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

None of these

Lower

Higher

Same

30. During dehumidification process, the relative humidity

Remains constant

None of these

Decreases

Increases

Page 4 of 4

31. 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

32. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Carbon dioxide

Ammonia

33. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

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

Atmospheric pressure

24 bars

56 bars

Slightly above atmospheric pressure

35. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

36. During humidification process, __________ increases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

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

Increase

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

38. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Cooling below 0°C

Very little power consumption

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

Dehumidification

Humidification

Heating and humidification

Cooling and dehumidification

40. 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

Degree of saturation

Humidity ratio

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Refrigeration & Air-Conditioning Practice Set-1

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