Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. During humidification process, dry bulb temperature

Decreases

None of these

Remains constant

Increases

2. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

3. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

4. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

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

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

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

Capillary tube

Electrically operated throttling valve

Manually operated valve

Thermostatic valve

7. The refrigerant widely used in domestic refrigerators is

Ammonia

Carbon dioxide

R-12

Sulphur dioxide

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

Very wet vapour

Dry vapour

High pressure saturated liquid

Wet vapour

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

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Smelling

Using reagents

10. During dehumidification process, the relative humidity

Increases

Remains constant

Decreases

None of these

Page 2 of 4

11. Absorption system normally uses the following refrigerant

CO2

Freon-11

Ammonia

Freon-22

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

Zero

0.5

0.75

1.0

13. 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

14. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Very little power consumption

Cooling below 0°C

15. 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

16. 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

17. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

Could be anything

18. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Ammonia, water and hydrogen

Water and hydrogen

19. 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

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

20. 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

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

High pressure side close to receiver

Suction of compressor

22. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

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

Atmospheric pressure

56 bars

Slightly above atmospheric pressure

24 bars

24. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

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

Zero

100

50

20

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

More/less depending on size of plant

More

Less

Same

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

Depends on other factors

Decreases

Increases

Remain same

28. During humidification process, __________ increases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

29. 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

30. 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 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.

Page 4 of 4

31. The moisture in a refrigerant is removed by

Evaporator

Safety relief valve

Driers

Dehumidifier

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

Bright green

Yellow

Orange

Red

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

Condenser

Expansion valve

Compressor

Evaporator

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

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

Remain unaffected

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

Expansion valve

Evaporator

Condenser

Compressor

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

R-12

CO₂

Ammonia

All of these

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

Saturated liquid

Wet vapour

Superheated vapour

Dry saturated vapour

38. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

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

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

40. 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.

Refrigeration & Air-Conditioning Practice Set-1

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