Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Wet vapour

Superheated vapour

Saturated liquid

Dry saturated vapour

2. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

3. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

4. 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

Dry bulb temperature

None of these

Dew point temperature

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

Same

Higher

None of these

Lower

6. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Quiet operation

Cooling below 0°C

7. During humidification process, __________ increases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

8. Which of the following statement is correct?

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.

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.

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

Capillary tube

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

10. Which of the following statement is wrong?

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.

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

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

Red

Yellow

Bright green

Orange

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

Condenser

Compressor

Evaporator

Expansion valve

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

Suction of compressor

Low pressure side near receiver

Delivery of compressor

High pressure side close to receiver

14. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Carbon dioxide

Sulphur dioxide

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

Atmospheric pressure

24 bars

Slightly above atmospheric pressure

56 bars

16. One ton refrigeration corresponds to

50 kcal/ hr

50 kcal/ min

80 kcal/ hr

80 kcal/ min

17. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

18. 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

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

1.0

0.75

Zero

0.5

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

Evaporator

Condenser

Expansion valve

Compressor

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21. 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

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

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

Remain unaffected

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

Dehumidification

Heating and humidification

Humidification

Cooling and dehumidification

24. Absorption system normally uses the following refrigerant

Ammonia

Freon-22

CO2

Freon-11

25. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

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

Increases

Depends on other factors

Remain same

Decreases

27. 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

28. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Safety relief valve

Driers

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

R-12

CO₂

All of these

Ammonia

30. 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 plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

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31. During dehumidification process, the relative humidity

Increases

Remains constant

None of these

Decreases

32. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

33. 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

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Smaller cabinet should be used

34. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

None of these

Ammonia and hydrogen

Water and hydrogen

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

Same

Less

More/less depending on size of plant

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

100

Zero

37. 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

38. 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

Absolute humidity

Degree of saturation

Relative humidity

Humidity ratio

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

Dry vapour

Wet vapour

High pressure saturated liquid

Very wet vapour

40. During humidification process, dry bulb temperature

Decreases

Remains constant

Increases

None of these

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Refrigeration & Air-Conditioning Practice Set-1

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