Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Increases C.O.P

C.O.P remains unaltered

Decreases C.O.P

2. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

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

Slightly above atmospheric pressure

24 bars

Atmospheric pressure

56 bars

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

After passing through the condenser

Before passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

5. 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

Increase

Decrease

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

Humidification

Cooling and dehumidification

Dehumidification

Heating and humidification

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

Halide torch which on detection produces greenish flame lighting

Smelling

Using reagents

Sulphur sticks which on detection gives white smoke

8. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

9. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

10. 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

Dew point temperature

None of these

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11. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

None of these

Ammonia and hydrogen

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

0.75

1.0

Zero

0.5

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

Evaporator

Compressor

Expansion valve

Condenser

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

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

15. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Driers

Safety relief valve

16. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

17. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

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

Remain same

Depends on other factors

Decreases

Increases

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

More/less depending on size of plant

Less

Same

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

Dry saturated vapour

Wet vapour

Saturated liquid

Superheated vapour

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21. During dehumidification process, the relative humidity

Decreases

None of these

Increases

Remains constant

22. The refrigerant widely used in domestic refrigerators is

Ammonia

Sulphur dioxide

Carbon dioxide

R-12

23. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

24. Which of the following statement is wrong?

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.

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

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

Evaporator

Compressor

Expansion valve

Condenser

26. 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

Relative humidity

Degree of saturation

Humidity ratio

Absolute humidity

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

100

Zero

28. Which of the following statement is correct?

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

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.

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

29. During humidification process, dry bulb temperature

None of these

Decreases

Increases

Remains constant

30. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Cooling below 0°C

Very little power consumption

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31. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ min

80 kcal/ hr

50 kcal/ hr

32. 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

33. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

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

None of these

Higher

Same

Lower

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

R-12

CO₂

All of these

Ammonia

36. 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

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

Very wet vapour

Wet vapour

Dry vapour

High pressure saturated liquid

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

Manually operated valve

Electrically operated throttling valve

Capillary tube

Thermostatic valve

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

Orange

Yellow

Bright green

Red

40. During sensible heating of air _________ decreases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

Refrigeration & Air-Conditioning Practice Set-1

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