Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

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

0.5

Zero

1.0

0.75

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

Expansion valve

Condenser

Evaporator

Compressor

4. Absorption system normally uses the following refrigerant

Freon-11

CO2

Freon-22

Ammonia

5. 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

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

6. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ hr

80 kcal/ min

50 kcal/ min

7. 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

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

Increases

Decreases

Depends on other factors

Remain same

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

Electrically operated throttling valve

Capillary tube

Manually operated valve

Thermostatic valve

10. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

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11. Which of the following statement is correct?

All of these

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.

In vapour absorption refrigerator, the compression of refrigerant is avoided.

12. 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

13. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Driers

Evaporator

14. 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

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

Compressor

Expansion valve

Condenser

Evaporator

16. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

17. During sensible cooling of air ________ decreases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

18. 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

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

100

Zero

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

Halide torch which on detection produces greenish flame lighting

Using reagents

Sulphur sticks which on detection gives white smoke

Smelling

Page 3 of 4

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

Yellow

Red

Bright green

Orange

22. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

23. During humidification process, __________ increases.

Specific humidity

Wet bulb temperature

Relative humidity

Dry bulb temperature

24. 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

25. 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

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

None of these

Lower

Higher

Same

27. 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

Dew point temperature

Wet bulb temperature

None of these

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

Wet vapour

High pressure saturated liquid

Very wet vapour

Dry vapour

29. Pick up the incorrect statement

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

Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

30. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Cooling below 0°C

Noisy operation

Page 4 of 4

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

Wet vapour

Superheated vapour

Saturated liquid

Dry saturated vapour

32. During sensible heating of air _________ decreases.

Specific humidity

Wet bulb temperature

Dry bulb temperature

Relative humidity

33. During humidification process, dry bulb temperature

None of these

Increases

Decreases

Remains constant

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

Dehumidification

Humidification

Cooling and dehumidification

Heating and humidification

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

High pressure side close to receiver

Suction of compressor

Delivery of compressor

Low pressure side near receiver

36. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

37. 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.

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

Less

Same

More/less depending on size of plant

39. During dehumidification process, the relative humidity

None of these

Decreases

Remains constant

Increases

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

R-12

Ammonia

CO₂

All of these

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Refrigeration & Air-Conditioning Practice Set-1

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