Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

20

Zero

50

100

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

All of these

CO₂

Ammonia

R-12

4. During humidification process, dry bulb temperature

Increases

None of these

Decreases

Remains constant

5. 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

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

Thermostatic valve

Electrically operated throttling valve

Capillary tube

Manually operated valve

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

After passing through the expansion throttle valve

After passing through the condenser

Before entering the expansion valve

Before passing through the condenser

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

Compressor

Condenser

Expansion valve

Evaporator

9. Chaperon equation is a relation between

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

10. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

Page 2 of 4

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

Expansion valve

Evaporator

Condenser

Compressor

12. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

13. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

50 kcal/ min

14. Absorption system normally uses the following refrigerant

Freon-11

Ammonia

Freon-22

CO2

15. During dehumidification process, the relative humidity

None of these

Increases

Decreases

Remains constant

16. 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.

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

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

17. 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

18. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

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

Higher

None of these

Same

Lower

20. Under cooling in a refrigeration cycle

Increases C.O.P

Decreases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Page 3 of 4

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

Perfectly tight vapour seal should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

22. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

23. 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 low condensing pressures

Large displacements and high condensing pressures

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

25. 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

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

0.75

Zero

0.5

1.0

27. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

28. 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

Wet bulb temperature

None of these

Dry bulb temperature

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

Suction of compressor

High pressure side close to receiver

Delivery of compressor

Low pressure side near receiver

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

24 bars

56 bars

Slightly above atmospheric pressure

Atmospheric pressure

Page 4 of 4

31. 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.

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

Bright green

Yellow

Red

Orange

33. Pick up the incorrect statement

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

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

34. During humidification process, __________ increases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

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

Same

More/less depending on size of plant

Less

More

36. 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

Humidity ratio

Absolute humidity

Relative humidity

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

Cooling and dehumidification

Humidification

Heating and humidification

Dehumidification

38. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

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

Decreases

Depends on other factors

Remain same

Increases

40. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Very little power consumption

Noisy operation

Refrigeration & Air-Conditioning Practice Set-1

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