Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

1.0

0.75

Zero

0.5

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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

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

Increases

Depends on other factors

Remain same

Decreases

4. 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

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

Dry bulb temperature

Wet bulb temperature

None of these

Dew point temperature

6. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

7. Absorption system normally uses the following refrigerant

CO2

Freon-11

Freon-22

Ammonia

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

Atmospheric pressure

Slightly above atmospheric pressure

56 bars

24 bars

9. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Very little power consumption

Quiet operation

Noisy operation

10. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

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11. 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.

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.

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

CO₂

All of these

Ammonia

R-12

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

Heating and humidification

Cooling and dehumidification

Dehumidification

Humidification

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

50

100

Zero

20

15. During humidification process, dry bulb temperature

Remains constant

None of these

Increases

Decreases

16. Which of the following statement is correct?

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.

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

All of these

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

Manually operated valve

Electrically operated throttling valve

Thermostatic valve

Capillary tube

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

Compressor

Expansion valve

Evaporator

Condenser

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

Condenser

Expansion valve

Compressor

Evaporator

20. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

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21. Under cooling in a refrigeration cycle

Increases C.O.P

C.O.P remains unaltered

Decreases C.O.P

Other factors decide C.O.P

22. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

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

Same

More/less depending on size of plant

Less

More

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

Red

Orange

Yellow

Bright green

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

Dry saturated vapour

Wet vapour

Saturated liquid

Superheated vapour

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

After passing through the expansion throttle valve

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

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

Wet vapour

Very wet vapour

Dry vapour

High pressure saturated liquid

28. During dehumidification process, the relative humidity

None of these

Decreases

Increases

Remains constant

29. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

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

Sulphur sticks which on detection gives white smoke

Smelling

Halide torch which on detection produces greenish flame lighting

Using reagents

Page 4 of 4

31. 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

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

High pressure side close to receiver

Suction of compressor

Delivery of compressor

Low pressure side near receiver

33. The vapour pressure of refrigerant should be

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

34. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

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

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

36. 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 used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

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

May increase or decrease depending on the type of refrigerant used

Remain unaffected

Decrease

Increase

38. 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

39. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

40. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Carbon dioxide

Ammonia

Refrigeration & Air-Conditioning Practice Set-1

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