Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. During humidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

2. 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

3. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

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

Superheated vapour

Saturated liquid

Dry saturated vapour

Wet vapour

5. 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 high condensing pressures

Small displacements and low condensing pressures

6. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Water and hydrogen

Ammonia, water and hydrogen

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

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Suction of compressor

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

Evaporator

Compressor

Condenser

Expansion valve

9. 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

10. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

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11. Which of the following statement is wrong?

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.

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.

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

Thermostatic valve

Electrically operated throttling valve

Capillary tube

Manually operated valve

13. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

14. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

80 kcal/ min

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

Smelling

Halide torch which on detection produces greenish flame lighting

Using reagents

Sulphur sticks which on detection gives white smoke

16. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Dehumidifier

Evaporator

17. Pick up the incorrect statement

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

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

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

Higher

None of these

Lower

Same

19. 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

Dry bulb temperature

Dew point temperature

Wet bulb temperature

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

Condenser

Evaporator

Compressor

Expansion valve

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

Perfectly tight vapour seal should be used

Smaller cabinet should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

22. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Decreases C.O.P

Increases C.O.P

23. Which of the following statement is correct?

All of these

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.

24. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Wet bulb temperature

Relative humidity

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

Atmospheric pressure

56 bars

24 bars

Slightly above atmospheric pressure

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

May increase or decrease depending on the type of refrigerant used

Remain unaffected

Increase

Decrease

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

Remain same

Decreases

Depends on other factors

Increases

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

Zero

100

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

Same

More/less depending on size of plant

Less

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

0.75

Zero

1.0

0.5

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31. Absorption system normally uses the following refrigerant

CO2

Freon-22

Freon-11

Ammonia

32. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

33. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

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

Yellow

Bright green

Red

Orange

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

Humidification

Cooling and dehumidification

Dehumidification

Heating and humidification

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

CO₂

Ammonia

All of these

R-12

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

Wet vapour

Very wet vapour

Dry vapour

High pressure saturated liquid

38. During sensible cooling of air ________ decreases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

39. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Carbon dioxide

Sulphur dioxide

40. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Very little power consumption

Noisy operation

Refrigeration & Air-Conditioning Practice Set-1

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