Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. 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

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

2. During sensible cooling of air ________ decreases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

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

Using reagents

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Smelling

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

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Decrease

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

After passing through the expansion throttle valve

Before entering the expansion valve

After passing through the condenser

Before passing through the condenser

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

56 bars

24 bars

Slightly above atmospheric pressure

Atmospheric pressure

7. During humidification process, dry bulb temperature

Decreases

Increases

None of these

Remains constant

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

Capillary tube

Thermostatic valve

Electrically operated throttling valve

Manually operated valve

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

Superheated vapour

Dry saturated vapour

Saturated liquid

Wet vapour

10. An important characteristic of absorption system of refrigeration is

Noisy operation

Very little power consumption

Quiet operation

Cooling below 0°C

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

Delivery of compressor

High pressure side close to receiver

Suction of compressor

Low pressure side near receiver

12. 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

13. Which of the following statement is wrong?

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

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.

In vapour compression cycle, the useful part of the heat transfer is at the condenser.

14. 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

15. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

16. 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

Wet bulb temperature

None of these

Dew point temperature

17. 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

18. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

19. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

20. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Water and hydrogen

Ammonia, water and hydrogen

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21. The moisture in a refrigerant is removed by

Driers

Evaporator

Safety relief valve

Dehumidifier

22. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

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

Increases

Depends on other factors

Remain same

Decreases

24. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

25. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

50 kcal/ min

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

Same

Less

More/less depending on size of plant

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

Red

Orange

Yellow

Bright green

28. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Decreases C.O.P

C.O.P remains unaltered

Increases C.O.P

29. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

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

Zero

0.75

1.0

0.5

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31. 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.

All of these

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

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

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

100

Zero

33. 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

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

Expansion valve

Evaporator

Compressor

Condenser

35. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Sulphur dioxide

Carbon dioxide

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

Condenser

Expansion valve

Compressor

Evaporator

37. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-22

Freon-11

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

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

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

R-12

All of these

CO₂

Ammonia

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

Cooling and dehumidification

Dehumidification

Heating and humidification

Humidification

Refrigeration & Air-Conditioning Practice Set-1

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