Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Compressor

Evaporator

Condenser

Expansion valve

2. An important characteristic of absorption system of refrigeration is

Noisy operation

Quiet operation

Very little power consumption

Cooling below 0°C

3. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

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

Expansion valve

Compressor

Condenser

Evaporator

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

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Smaller cabinet should be used

6. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

7. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

8. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

50 kcal/ min

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

Increases

Decreases

Remain same

Depends on other factors

10. 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

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

Yellow

Orange

Bright green

Red

12. During sensible cooling of air ________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

13. 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.

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

Remain unaffected

Increase

Decrease

May increase or decrease depending on the type of refrigerant used

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

Same

Lower

None of these

Higher

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

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

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

Zero

0.75

1.0

0.5

18. During humidification process, dry bulb temperature

None of these

Increases

Remains constant

Decreases

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

Ammonia

CO₂

All of these

R-12

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

Zero

100

Page 3 of 4

21. During sensible heating of air _________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

22. The refrigerant widely used in domestic refrigerators is

Ammonia

Sulphur dioxide

Carbon dioxide

R-12

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

Very wet vapour

Wet vapour

Dry vapour

High pressure saturated liquid

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

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

25. Absorption system normally uses the following refrigerant

Freon-22

CO2

Freon-11

Ammonia

26. 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

Humidity ratio

Absolute humidity

Relative humidity

Degree of saturation

27. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

28. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

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

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Suction of compressor

30. During humidification process, __________ increases.

Relative humidity

Dry bulb temperature

Specific humidity

Wet bulb temperature

Page 4 of 4

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

Wet vapour

Saturated liquid

Dry saturated vapour

Superheated vapour

32. The moisture in a refrigerant is removed by

Safety relief valve

Driers

Evaporator

Dehumidifier

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

After passing through the expansion throttle valve

Before passing through the condenser

After passing through the condenser

Before entering the expansion valve

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

Same

Less

More/less depending on size of plant

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

56 bars

24 bars

Atmospheric pressure

Slightly above atmospheric pressure

36. Which of the following statement is wrong?

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.

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.

37. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

Increases C.O.P

C.O.P remains unaltered

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

Capillary tube

Thermostatic valve

Manually operated valve

Electrically operated throttling valve

39. 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

40. 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

Refrigeration & Air-Conditioning Practice Set-1

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