Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

2. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

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

Degree of saturation

Humidity ratio

Relative humidity

Absolute humidity

4. 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

None of these

Dry bulb temperature

5. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Ammonia, water and hydrogen

Water and hydrogen

None of these

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

Heating and humidification

Cooling and dehumidification

Dehumidification

Humidification

7. Pick up the incorrect statement

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

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

8. An important characteristic of absorption system of refrigeration is

Noisy operation

Very little power consumption

Cooling below 0°C

Quiet operation

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

High pressure side close to receiver

Suction of compressor

Delivery of compressor

Low pressure side near receiver

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

Evaporator

Expansion valve

Compressor

Condenser

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11. The moisture in a refrigerant is removed by

Driers

Evaporator

Safety relief valve

Dehumidifier

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

Remain same

Decreases

Increases

Depends on other factors

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

Higher

Lower

None of these

Same

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

0.5

0.75

Zero

1.0

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

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

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

Wet vapour

High pressure saturated liquid

Very wet vapour

Dry vapour

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

CO₂

All of these

R-12

Ammonia

18. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

19. During humidification process, dry bulb temperature

Remains constant

Decreases

None of these

Increases

20. Which of the following statement is correct?

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

All of these

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.

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21. 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.

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.

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

Yellow

Red

Orange

Bright green

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

24 bars

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

24. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

25. 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

26. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

27. During dehumidification process, the relative humidity

None of these

Remains constant

Decreases

Increases

28. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

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

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

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

After passing through the expansion throttle valve

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

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31. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

50 kcal/ min

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

Less

More/less depending on size of plant

Same

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

Dry saturated vapour

Superheated vapour

Wet vapour

Saturated liquid

34. During sensible heating of air _________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

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

Condenser

Evaporator

Compressor

Expansion valve

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

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Increase

37. 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

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

Capillary tube

Manually operated valve

Electrically operated throttling valve

Thermostatic valve

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

100

Zero

40. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

CO2

Ammonia

Refrigeration & Air-Conditioning Practice Set-1

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