Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Before passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

After passing through the condenser

2. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Noisy operation

Very little power consumption

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

100

Zero

4. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Driers

Evaporator

5. 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

Relative humidity

Degree of saturation

Absolute humidity

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

More/less depending on size of plant

Less

Same

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

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

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

Heating and humidification

Dehumidification

Cooling and dehumidification

Humidification

9. Absorption system normally uses the following refrigerant

CO2

Freon-22

Freon-11

Ammonia

10. 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

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Smaller cabinet should be used

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11. 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

12. Under cooling in a refrigeration cycle

Other factors decide C.O.P

C.O.P remains unaltered

Decreases C.O.P

Increases C.O.P

13. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

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

Very wet vapour

Wet vapour

High pressure saturated liquid

Dry vapour

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

Compressor

Expansion valve

Evaporator

Condenser

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

CO₂

R-12

All of these

Ammonia

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

Compressor

Condenser

Expansion valve

Evaporator

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

Delivery of compressor

Low pressure side near receiver

High pressure side close to receiver

Suction of compressor

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

Wet bulb temperature

Dew point temperature

None of these

Dry bulb temperature

20. 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

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

Wet vapour

Dry saturated vapour

Superheated vapour

Saturated liquid

22. During sensible cooling of air ________ decreases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

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

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Decrease

Increase

24. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

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

Thermostatic valve

Capillary tube

Manually operated valve

Electrically operated throttling valve

26. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

27. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Carbon dioxide

Sulphur dioxide

28. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

29. Which of the following statement is correct?

Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.

All of these

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.

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

Remain same

Depends on other factors

Decreases

Increases

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31. Pick up the incorrect statement

A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

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

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

56 bars

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

Zero

1.0

0.5

0.75

34. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

35. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

Red

Yellow

Orange

Bright green

37. 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.

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

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

38. 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

39. The vapour pressure of refrigerant should be

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

40. During humidification process, dry bulb temperature

Remains constant

Increases

None of these

Decreases

Refrigeration & Air-Conditioning Practice Set-1

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