Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Ammonia, water and hydrogen

None of these

Water and hydrogen

2. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Very little power consumption

Cooling below 0°C

3. During sensible heating of air _________ decreases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

4. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

5. 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

Degree of saturation

Relative humidity

Humidity ratio

Absolute humidity

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

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

Delivery of compressor

7. Which of the following statement is wrong?

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.

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.

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

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

R-12

All of these

Ammonia

CO₂

10. The moisture in a refrigerant is removed by

Safety relief valve

Driers

Evaporator

Dehumidifier

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11. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

12. During sensible cooling of air ________ decreases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

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

Dry vapour

High pressure saturated liquid

Very wet vapour

Wet vapour

14. 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 low condensing pressures

Small displacements and high condensing pressures

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

24 bars

Atmospheric pressure

Slightly above atmospheric pressure

56 bars

16. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

17. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

CO2

Ammonia

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

Dew point temperature

None of these

Wet bulb temperature

Dry bulb temperature

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

Cooling and dehumidification

Heating and humidification

Humidification

Dehumidification

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

0.75

Zero

0.5

1.0

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21. 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

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

50

Zero

20

100

23. 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

24. 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

25. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Lower than atmospheric pressure

Higher than atmospheric pressure

Could be anything

26. During humidification process, dry bulb temperature

Increases

None of these

Remains constant

Decreases

27. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Carbon dioxide

Ammonia

R-12

28. During dehumidification process, the relative humidity

Decreases

Remains constant

None of these

Increases

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

Higher

None of these

Lower

Same

30. Which of the following statement is correct?

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.

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

Page 4 of 4

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

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

After passing through the condenser

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

More

Same

Less

More/less depending on size of plant

33. During humidification process, __________ increases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

34. 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

Increase

Remain unaffected

Decrease

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

Orange

Bright green

Red

Yellow

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

Evaporator

Compressor

Expansion valve

Condenser

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

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

Capillary tube

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

Decreases

Depends on other factors

Remain same

Increases

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

Compressor

Evaporator

Expansion valve

Condenser

40. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

Refrigeration & Air-Conditioning Practice Set-1

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