Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Bright green

Yellow

Orange

Red

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

20

50

Zero

100

4. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

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

Compressor

Condenser

Evaporator

Expansion valve

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

Cooling and dehumidification

Heating and humidification

Dehumidification

Humidification

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

Ammonia

R-12

All of these

CO₂

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

Halide torch which on detection produces greenish flame lighting

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

9. 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

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

Lower

Same

None of these

Higher

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11. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

80 kcal/ min

12. 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

Lithium bromide used in vapour absorption cycle is non volatile

A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

13. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

14. The refrigerant widely used in domestic refrigerators is

Ammonia

Sulphur dioxide

Carbon dioxide

R-12

15. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

16. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

Increases

Decreases

Remain same

Depends on other factors

18. 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

19. Which of the following statement is wrong?

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

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

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.

20. 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

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

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21. 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

22. 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

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

Before passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

After passing through the condenser

24. During sensible cooling of air ________ decreases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

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

More

More/less depending on size of plant

Less

Same

26. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia, water and hydrogen

Ammonia and hydrogen

27. 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

Dry bulb temperature

Dew point temperature

None of these

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

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

29. 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

Relative humidity

Degree of saturation

Absolute humidity

Humidity ratio

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

Wet vapour

High pressure saturated liquid

Dry vapour

Very wet vapour

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

0.75

1.0

Zero

0.5

32. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

33. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

CO2

Ammonia

34. An important characteristic of absorption system of refrigeration is

Noisy operation

Very little power consumption

Quiet operation

Cooling below 0°C

35. 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

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

Evaporator

Condenser

Compressor

Expansion valve

37. During humidification process, dry bulb temperature

None of these

Remains constant

Increases

Decreases

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

39. Which of the following statement is correct?

All of these

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.

In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.

40. During dehumidification process, the relative humidity

Increases

None of these

Decreases

Remains constant

Refrigeration & Air-Conditioning Practice Set-1

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