Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. During humidification process, __________ increases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

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

0.5

1.0

0.75

Zero

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

Delivery of compressor

Low pressure side near receiver

High pressure side close to receiver

Suction of compressor

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

Remain same

Decreases

Increases

Depends on other factors

5. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Carbon dioxide

Ammonia

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

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

7. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

8. The moisture in a refrigerant is removed by

Dehumidifier

Driers

Safety relief valve

Evaporator

9. 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

Humidity ratio

Degree of saturation

Relative humidity

10. Absorption system normally uses the following refrigerant

CO2

Ammonia

Freon-11

Freon-22

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11. 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

None of these

Dry bulb temperature

Dew point temperature

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

Zero

50

20

100

13. Pick up the incorrect statement

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

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

Lithium bromide used in vapour absorption cycle is non volatile

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

Before passing through the condenser

After passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

15. During humidification process, dry bulb temperature

Decreases

None of these

Remains constant

Increases

16. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

17. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

50 kcal/ min

18. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

19. Which of the following statement is correct?

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.

All of these

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

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

Saturated liquid

Superheated vapour

Wet vapour

Dry saturated vapour

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

Thermostatic valve

Electrically operated throttling valve

Manually operated valve

Capillary tube

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

CO₂

Ammonia

R-12

All of these

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

Atmospheric pressure

56 bars

24 bars

Slightly above atmospheric pressure

24. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Ammonia, water and hydrogen

Water and hydrogen

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

Higher

None of these

Same

Lower

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

High pressure saturated liquid

Wet vapour

Very wet vapour

Dry vapour

27. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Increases C.O.P

Other factors decide C.O.P

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

Cooling and dehumidification

Dehumidification

Humidification

Heating and humidification

29. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

30. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

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31. An important characteristic of absorption system of refrigeration is

Noisy operation

Quiet operation

Cooling below 0°C

Very little power consumption

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

Red

Orange

Bright green

Yellow

33. Which of the following statement is wrong?

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 ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

In vapour compression cycle, the useful part of the heat transfer is at the condenser.

34. During dehumidification process, the relative humidity

Remains constant

None of these

Decreases

Increases

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

Evaporator

Compressor

Expansion valve

Condenser

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

More

Less

Same

More/less depending on size of plant

37. 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

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

Evaporator

Compressor

Expansion valve

Condenser

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

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

40. 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

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Refrigeration & Air-Conditioning Practice Set-1

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