Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

2. 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

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

R-12

CO₂

All of these

Ammonia

4. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

50 kcal/ min

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

Evaporator

Expansion valve

Condenser

Compressor

6. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia and hydrogen

Ammonia, water and hydrogen

7. The moisture in a refrigerant is removed by

Safety relief valve

Driers

Dehumidifier

Evaporator

8. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

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

Depends on other factors

Increases

Remain same

Decreases

10. Pick up the incorrect statement

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

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

Page 2 of 4

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

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

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

Orange

Bright green

Yellow

Red

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

56 bars

Atmospheric pressure

24 bars

Slightly above atmospheric pressure

14. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called

Dry bulb temperature

None of these

Wet bulb temperature

Dew point temperature

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

Wet vapour

Dry saturated vapour

Saturated liquid

Superheated vapour

16. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

After passing through the expansion throttle valve

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

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

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

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

Zero

100

20. During sensible cooling of air ________ decreases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

Page 3 of 4

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

High pressure saturated liquid

Dry vapour

Very wet vapour

Wet vapour

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

Humidification

Heating and humidification

Dehumidification

Cooling and dehumidification

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

Sulphur sticks which on detection gives white smoke

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

24. Which of the following statement is wrong?

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

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

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

0.75

Zero

0.5

1.0

26. During humidification process, dry bulb temperature

Remains constant

Decreases

None of these

Increases

27. 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

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

More/less depending on size of plant

Same

Less

29. During humidification process, __________ increases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

30. During dehumidification process, the relative humidity

Decreases

Increases

None of these

Remains constant

Page 4 of 4

31. Which of the following statement is correct?

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.

All of these

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

Condenser

Evaporator

Expansion valve

Compressor

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

None of these

Same

Higher

Lower

34. Absorption system normally uses the following refrigerant

Freon-11

CO2

Freon-22

Ammonia

35. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

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

High pressure side close to receiver

Low pressure side near receiver

Delivery of compressor

Suction of compressor

37. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Very little power consumption

Cooling below 0°C

38. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Ammonia

Sulphur dioxide

R-12

39. 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

Relative humidity

Absolute humidity

40. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Decreases C.O.P

Increases C.O.P

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Refrigeration & Air-Conditioning Practice Set-1

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