Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

Ammonia

R-12

2. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

3. Pick up the incorrect statement

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

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

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

High pressure side close to receiver

Suction of compressor

Low pressure side near receiver

Delivery of compressor

5. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

6. Absorption system normally uses the following refrigerant

Freon-11

Freon-22

Ammonia

CO2

7. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Lower than atmospheric pressure

Could be anything

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

Compressor

Condenser

Evaporator

Expansion valve

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

Dehumidification

Humidification

Heating and humidification

Cooling and dehumidification

10. An important characteristic of absorption system of refrigeration is

Very little power consumption

Cooling below 0°C

Noisy operation

Quiet operation

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11. 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

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

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

All of these

CO₂

R-12

Ammonia

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

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

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

Red

Yellow

Orange

Bright green

15. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

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

Remain same

Decreases

Increases

Depends on other factors

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

Less

More/less depending on size of plant

Same

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

Manually operated valve

Thermostatic valve

Electrically operated throttling valve

Capillary tube

19. 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.

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.

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

Wet vapour

Very wet vapour

High pressure saturated liquid

Dry vapour

Page 3 of 4

21. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Driers

Evaporator

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

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

23. During sensible cooling of air ________ decreases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

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

100

Zero

25. Which of the following statement is correct?

All of these

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

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.

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

Same

None of these

Higher

Lower

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

Expansion valve

Compressor

Condenser

Evaporator

28. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called

None of these

Dry bulb temperature

Dew point temperature

Wet bulb temperature

29. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

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

56 bars

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

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31. 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

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

Wet vapour

Superheated vapour

Saturated liquid

Dry saturated vapour

33. During humidification process, __________ increases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

34. 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

Relative humidity

Humidity ratio

Degree of saturation

35. During humidification process, dry bulb temperature

Remains constant

None of these

Decreases

Increases

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

1.0

0.75

0.5

Zero

37. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

38. 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

39. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Ammonia, water and hydrogen

Water and hydrogen

None of these

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

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Using reagents

Smelling

Refrigeration & Air-Conditioning Practice Set-1

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