Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

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

More/less depending on size of plant

Same

Less

3. 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

Degree of saturation

Relative humidity

4. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

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

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

Delivery of compressor

6. During humidification process, __________ increases.

Dry bulb temperature

Specific humidity

Wet bulb temperature

Relative humidity

7. Which of the following statement is wrong?

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.

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.

8. 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

Perfectly tight vapour seal should be used

Smaller cabinet should be used

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

0.5

0.75

1.0

Zero

10. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Driers

Dehumidifier

Page 2 of 4

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

Orange

Yellow

Red

Bright green

12. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Cooling below 0°C

Very little power consumption

13. One ton refrigeration corresponds to

50 kcal/ min

80 kcal/ min

50 kcal/ hr

80 kcal/ hr

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

High pressure saturated liquid

Very wet vapour

Wet vapour

Dry vapour

15. During humidification process, dry bulb temperature

Remains constant

None of these

Increases

Decreases

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

Electrically operated throttling valve

Thermostatic valve

Capillary tube

Manually operated valve

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

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

Zero

100

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

Ammonia

All of these

R-12

CO₂

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

Slightly above atmospheric pressure

56 bars

Atmospheric pressure

24 bars

Page 3 of 4

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

Humidification

Dehumidification

Heating and humidification

Cooling and dehumidification

22. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

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

Dry bulb temperature

None of these

Dew point temperature

Wet bulb temperature

24. Which of the following statement is correct?

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

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.

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

Evaporator

Expansion valve

Condenser

Compressor

26. During sensible heating of air _________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

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

Before entering the expansion valve

After passing through the expansion throttle valve

After passing through the condenser

Before passing through the condenser

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

Compressor

Condenser

Expansion valve

Evaporator

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

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

Halide torch which on detection produces greenish flame lighting

30. The refrigerant widely used in domestic refrigerators is

R-12

Sulphur dioxide

Ammonia

Carbon dioxide

Page 4 of 4

31. 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

32. During dehumidification process, the relative humidity

Increases

None of these

Decreases

Remains constant

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

Superheated vapour

Wet vapour

Dry saturated vapour

Saturated liquid

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

Decrease

May increase or decrease depending on the type of refrigerant used

Increase

Remain unaffected

35. During sensible cooling of air ________ decreases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

36. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

37. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

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

38. The vapour pressure of refrigerant should be

Could be anything

Lower than atmospheric pressure

Higher than atmospheric pressure

Equal to atmospheric pressure

39. Absorption system normally uses the following refrigerant

CO2

Freon-22

Ammonia

Freon-11

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

Increases

Remain same

Depends on other factors

Decreases

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Refrigeration & Air-Conditioning Practice Set-1

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