Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Higher

Same

Lower

None of these

2. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ min

80 kcal/ hr

50 kcal/ min

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

CO₂

Ammonia

All of these

R-12

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

Less

More/less depending on size of plant

Same

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

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

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

Saturated liquid

Superheated vapour

Dry saturated vapour

Wet vapour

7. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia and hydrogen

Ammonia, water and hydrogen

8. During dehumidification process, the relative humidity

None of these

Remains constant

Increases

Decreases

9. Which of the following statement is wrong?

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.

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.

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

0.5

Zero

0.75

1.0

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11. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

12. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Evaporator

Driers

13. During sensible cooling of air ________ decreases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

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

Cooling and dehumidification

Dehumidification

Humidification

Heating and humidification

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

Dew point temperature

Dry bulb temperature

None of these

Wet bulb temperature

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

Zero

100

18. 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

Degree of saturation

Relative humidity

Absolute humidity

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

Decrease

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

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

High pressure saturated liquid

Wet vapour

Dry vapour

Very wet vapour

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21. During humidification process, __________ increases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

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

Before passing through the condenser

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

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

Suction of compressor

Delivery of compressor

Low pressure side near receiver

High pressure side close to receiver

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

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

Capillary tube

25. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

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

Bright green

Orange

Red

Yellow

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

Expansion valve

Evaporator

Compressor

Condenser

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

Increases

Depends on other factors

Remain same

Decreases

29. Absorption system normally uses the following refrigerant

Ammonia

Freon-22

CO2

Freon-11

30. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

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 plant can't operate below 0°C

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31. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

32. 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

33. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

34. During humidification process, dry bulb temperature

None of these

Remains constant

Decreases

Increases

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

Slightly above atmospheric pressure

56 bars

Atmospheric pressure

24 bars

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

Evaporator

Condenser

Compressor

Expansion valve

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

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

Halide torch which on detection produces greenish flame lighting

38. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Noisy operation

Very little power consumption

39. 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.

40. 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

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

Refrigeration & Air-Conditioning Practice Set-1

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