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

None of these

Wet bulb temperature

Dry bulb temperature

Dew point temperature

2. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

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

Superheated vapour

Wet vapour

Dry saturated vapour

Saturated liquid

4. 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

5. 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

6. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

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

Lower

Higher

Same

None of these

8. 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

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

Remain unaffected

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

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

Ammonia

CO₂

All of these

R-12

Page 2 of 4

11. 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

Humidity ratio

Absolute humidity

Degree of saturation

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

20

50

Zero

100

13. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

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

Remain same

Increases

Decreases

Depends on other factors

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

Electrically operated throttling valve

Manually operated valve

Capillary tube

Thermostatic valve

16. Absorption system normally uses the following refrigerant

Freon-22

CO2

Freon-11

Ammonia

17. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

18. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

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

0.5

1.0

0.75

Zero

20. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Page 3 of 4

21. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

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

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

Delivery of compressor

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

High pressure saturated liquid

Very wet vapour

Dry vapour

Wet vapour

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

Orange

Yellow

Red

Bright green

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

24 bars

56 bars

Atmospheric pressure

Slightly above atmospheric pressure

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

After passing through the expansion throttle valve

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

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

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

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

More/less depending on size of plant

More

Same

Less

29. Which of the following statement is wrong?

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.

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.

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

Cooling and dehumidification

Heating and humidification

Humidification

Dehumidification

Page 4 of 4

31. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Very little power consumption

Quiet operation

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

Compressor

Condenser

Expansion valve

Evaporator

33. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Dehumidifier

Evaporator

34. During humidification process, __________ increases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

35. During humidification process, dry bulb temperature

None of these

Remains constant

Decreases

Increases

36. 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

37. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

Evaporator

Condenser

Compressor

Expansion valve

39. During dehumidification process, the relative humidity

Remains constant

Increases

None of these

Decreases

40. Which of the following statement is correct?

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

All of these

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.

Refrigeration & Air-Conditioning Practice Set-1

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