Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Noisy operation

Very little power consumption

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

Zero

100

3. The moisture in a refrigerant is removed by

Evaporator

Driers

Safety relief valve

Dehumidifier

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

Wet vapour

Dry saturated vapour

Superheated vapour

Saturated liquid

5. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

6. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

7. Absorption system normally uses the following refrigerant

CO2

Freon-11

Ammonia

Freon-22

8. During dehumidification process, the relative humidity

Remains constant

None of these

Increases

Decreases

9. One ton refrigeration corresponds to

50 kcal/ min

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

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

Delivery of compressor

Suction of compressor

High pressure side close to receiver

Low pressure side near receiver

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11. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

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

Decreases

Increases

Depends on other factors

Remain same

13. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Equal to atmospheric pressure

Lower than atmospheric pressure

14. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

Higher

Same

None of these

Lower

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

0.75

0.5

Zero

1.0

17. 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

Dry bulb temperature

None of these

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

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

After passing through the condenser

19. 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.

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

Manually operated valve

Capillary tube

Electrically operated throttling valve

Thermostatic valve

Page 3 of 4

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

Cooling and dehumidification

Dehumidification

Heating and humidification

Humidification

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

Compressor

Evaporator

Condenser

Expansion valve

23. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

24. During sensible heating of air _________ decreases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

25. During humidification process, dry bulb temperature

Decreases

Increases

Remains constant

None of these

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

Bright green

Yellow

Orange

Red

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

More/less depending on size of plant

Same

Less

28. 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

Dry vapour

Wet vapour

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

All of these

R-12

Ammonia

CO₂

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

Evaporator

Compressor

Condenser

Expansion valve

Page 4 of 4

31. 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

Absolute humidity

Relative humidity

Degree of saturation

Humidity ratio

32. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

33. Which of the following statement is wrong?

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.

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

34. Pick up the incorrect statement

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 plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

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

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Using reagents

36. 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

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

Increase

Remain unaffected

Decrease

May increase or decrease depending on the type of refrigerant used

38. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

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

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

40. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

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Refrigeration & Air-Conditioning Practice Set-1

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