Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. 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 used in vapour absorption cycle is non volatile

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

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

Condenser

Evaporator

Expansion valve

Compressor

3. 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

4. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-22

Freon-11

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

Expansion valve

Condenser

Compressor

Evaporator

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

Yellow

Orange

Red

Bright green

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

0.5

1.0

Zero

0.75

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. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

10. 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

Page 2 of 4

11. During humidification process, dry bulb temperature

Increases

None of these

Decreases

Remains constant

12. 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

13. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

14. 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.

15. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

R-12

Ammonia

16. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

17. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

18. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

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

Thermostatic valve

Manually operated valve

Capillary tube

Electrically operated throttling valve

20. During dehumidification process, the relative humidity

None of these

Remains constant

Decreases

Increases

Page 3 of 4

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

Low pressure side near receiver

Delivery of compressor

Suction of compressor

High pressure side close to receiver

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

100

Zero

50

20

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

Halide torch which on detection produces greenish flame lighting

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

24. 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

Humidity ratio

Relative humidity

Absolute humidity

Degree of saturation

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

Dry vapour

Wet vapour

High pressure saturated liquid

Very wet vapour

26. During humidification process, __________ increases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

27. Which of the following statement is correct?

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.

Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.

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

Saturated liquid

Wet vapour

Dry saturated vapour

Superheated vapour

29. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

30. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Dehumidifier

Evaporator

Page 4 of 4

31. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Decreases C.O.P

Other factors decide C.O.P

Increases C.O.P

32. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Noisy operation

Very little power consumption

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

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

34. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

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

Before passing through the condenser

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

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

Ammonia

All of these

R-12

CO₂

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

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

Remain same

Depends on other factors

Increases

Decreases

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

None of these

Wet bulb temperature

Dew point temperature

Dry bulb temperature

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

Less

More

More/less depending on size of plant

Same

Refrigeration & Air-Conditioning Practice Set-1

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