Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

2. Pick up the incorrect statement

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

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

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

Bright green

Red

Orange

Yellow

4. During dehumidification process, the relative humidity

Remains constant

Decreases

None of these

Increases

5. Which of the following statement is wrong?

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.

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.

6. During humidification process, dry bulb temperature

Increases

Remains constant

None of these

Decreases

7. 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

8. The moisture in a refrigerant is removed by

Dehumidifier

Driers

Evaporator

Safety relief valve

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

Expansion valve

Compressor

Condenser

Evaporator

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

Slightly above atmospheric pressure

24 bars

56 bars

Atmospheric pressure

Page 2 of 4

11. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

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

Humidification

Heating and humidification

Cooling and dehumidification

Dehumidification

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

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

14. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

15. 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

16. 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

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

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

Increases

Remain same

Depends on other factors

Decreases

18. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

19. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Carbon dioxide

Sulphur dioxide

20. 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

Page 3 of 4

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

R-12

All of these

CO₂

Ammonia

22. 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

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. 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

Absolute humidity

Humidity ratio

25. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

CO2

Ammonia

26. 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

27. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Increases C.O.P

Decreases C.O.P

Other factors decide C.O.P

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

Low pressure side near receiver

High pressure side close to receiver

Suction of compressor

Delivery of compressor

29. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

30. 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

Page 4 of 4

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

100

50

Zero

20

32. Which of the following statement is correct?

All of these

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.

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

33. The fluids used in Electrolux refrigerator are

None of these

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

34. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Compressor

Evaporator

Expansion valve

Condenser

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

Less

Same

More

More/less depending on size of plant

37. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Quiet operation

Very little power consumption

38. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

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

Superheated vapour

Wet vapour

Dry saturated vapour

Saturated liquid

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

0.5

Zero

1.0

0.75

Refrigeration & Air-Conditioning Practice Set-1

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