Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. 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

Dew point temperature

Wet bulb temperature

None of these

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

Saturated liquid

Wet vapour

Dry saturated vapour

Superheated vapour

3. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

Decrease

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

5. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

6. An important characteristic of absorption system of refrigeration is

Very little power consumption

Cooling below 0°C

Noisy operation

Quiet operation

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

Smelling

Halide torch which on detection produces greenish flame lighting

Using reagents

Sulphur sticks which on detection gives white smoke

8. 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

Smaller cabinet should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

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

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

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

Suction of compressor

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

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11. 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

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

Compressor

Expansion valve

Condenser

Evaporator

13. Absorption system normally uses the following refrigerant

Ammonia

Freon-22

Freon-11

CO2

14. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

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

Higher

Same

None of these

Lower

16. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

Ammonia

R-12

17. During sensible cooling of air ________ decreases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

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

Evaporator

Compressor

Condenser

Expansion valve

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

50

100

20

Zero

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

Thermostatic valve

Electrically operated throttling valve

Capillary tube

Manually operated valve

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

Very wet vapour

Dry vapour

High pressure saturated liquid

Wet vapour

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

R-12

Ammonia

CO₂

All of these

23. 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

24. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ min

80 kcal/ hr

50 kcal/ hr

25. Which of the following statement is correct?

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

All of these

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.

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

Cooling and dehumidification

Dehumidification

Heating and humidification

Humidification

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

Increases

Decreases

Depends on other factors

Remain same

28. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

29. Which of the following statement is wrong?

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

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

30. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

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

Less

Same

More

More/less depending on size of plant

32. The vapour pressure of refrigerant should be

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

33. Pick up the incorrect statement

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

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

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

After passing through the expansion throttle valve

Before entering the expansion valve

After passing through the condenser

Before passing through the condenser

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

0.75

1.0

Zero

0.5

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

24 bars

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

37. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

None of these

38. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

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

Orange

Bright green

Red

Yellow

40. During humidification process, dry bulb temperature

Decreases

None of these

Increases

Remains constant

Refrigeration & Air-Conditioning Practice Set-1

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