Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

Orange

Bright green

Yellow

Red

2. 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

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

Remain same

Depends on other factors

Increases

Decreases

4. Which of the following statement is wrong?

In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

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.

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

5. During humidification process, __________ increases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

6. During sensible cooling of air ________ decreases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

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

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

8. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Carbon dioxide

Ammonia

R-12

9. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Increases C.O.P

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

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

Page 2 of 4

11. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

12. Pick up the incorrect statement

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

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

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

Same

Less

More

More/less depending on size of plant

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

Condenser

Compressor

Expansion valve

Evaporator

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

Capillary tube

Thermostatic valve

Electrically operated throttling valve

Manually operated valve

16. Chaperon equation is a relation between

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

17. During dehumidification process, the relative humidity

Increases

Remains constant

None of these

Decreases

18. During humidification process, dry bulb temperature

Remains constant

Decreases

None of these

Increases

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

100

20

50

Zero

20. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

Page 3 of 4

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

Very wet vapour

Wet vapour

High pressure saturated liquid

Dry vapour

22. An important characteristic of absorption system of refrigeration is

Very little power consumption

Quiet operation

Noisy operation

Cooling below 0°C

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

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Using reagents

24. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Dehumidifier

Driers

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

Slightly above atmospheric pressure

24 bars

Atmospheric pressure

56 bars

26. 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

Dew point temperature

Dry bulb temperature

None of these

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

Ammonia

R-12

All of these

CO₂

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

Dehumidification

Heating and humidification

Cooling and dehumidification

Humidification

29. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Ammonia, water and hydrogen

Water and hydrogen

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

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Increase

Page 4 of 4

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

Evaporator

Expansion valve

Compressor

Condenser

32. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

Ammonia

CO2

33. 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

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

Higher

Lower

None of these

Same

35. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Lower than atmospheric pressure

Higher than atmospheric pressure

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

Saturated liquid

Dry saturated vapour

Superheated vapour

Wet vapour

37. 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

38. Which of the following statement is correct?

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.

All of these

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

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

Low pressure side near receiver

Suction of compressor

Delivery of compressor

High pressure side close to receiver

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

0.75

Zero

0.5

1.0

Refrigeration & Air-Conditioning Practice Set-1

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