Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

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

Expansion valve

Condenser

Compressor

Evaporator

2. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Wet bulb temperature

Relative humidity

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

Increases

Depends on other factors

Remain same

Decreases

4. 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

Dew point temperature

Dry bulb temperature

Wet bulb temperature

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

Zero

100

6. During sensible cooling of air ________ decreases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

7. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

8. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Increases C.O.P

C.O.P remains unaltered

Decreases C.O.P

9. 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

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

10. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

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11. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

12. 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

13. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Driers

Dehumidifier

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

Lower

None of these

Higher

Same

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

Increase

Decrease

May increase or decrease depending on the type of refrigerant used

Remain unaffected

16. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

17. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Quiet operation

Cooling below 0°C

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

Less

More/less depending on size of plant

Same

19. Which of the following statement is wrong?

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

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.

In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

20. The refrigerant widely used in domestic refrigerators is

R-12

Sulphur dioxide

Carbon dioxide

Ammonia

Page 3 of 4

21. During humidification process, __________ increases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

High pressure saturated liquid

Wet vapour

Very wet vapour

Dry vapour

23. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ min

50 kcal/ min

80 kcal/ hr

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

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

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

All of these

Ammonia

CO₂

R-12

26. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

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

Expansion valve

Evaporator

Compressor

Condenser

28. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

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

Lithium bromide used in vapour absorption cycle is non volatile

29. During dehumidification process, the relative humidity

None of these

Remains constant

Decreases

Increases

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

0.5

1.0

0.75

Zero

Page 4 of 4

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

Dehumidification

Heating and humidification

Cooling and dehumidification

Humidification

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

Superheated vapour

Dry saturated vapour

Saturated liquid

Wet vapour

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

Capillary tube

Thermostatic valve

Manually operated valve

Electrically operated throttling valve

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

After passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

Before passing through the condenser

35. 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

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

Absolute humidity

Humidity ratio

Degree of saturation

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

Yellow

Red

Bright green

Orange

38. During humidification process, dry bulb temperature

Increases

None of these

Remains constant

Decreases

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

Sulphur sticks which on detection gives white smoke

Using reagents

Halide torch which on detection produces greenish flame lighting

Smelling

40. Which of the following statement is correct?

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

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.

All of these

Refrigeration & Air-Conditioning Practice Set-1

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