Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Red

Yellow

Bright green

Orange

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

24 bars

Atmospheric pressure

56 bars

Slightly above atmospheric pressure

3. The refrigerant widely used in domestic refrigerators is

Ammonia

Sulphur dioxide

Carbon dioxide

R-12

4. During sensible heating of air _________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

5. 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

Relative humidity

Absolute humidity

Degree of saturation

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

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Increase

Decrease

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

Zero

100

8. Which of the following statement is wrong?

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.

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

9. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

Wet vapour

Dry vapour

Very wet vapour

High pressure saturated liquid

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11. During dehumidification process, the relative humidity

Decreases

None of these

Increases

Remains constant

12. Absorption system normally uses the following refrigerant

CO2

Freon-22

Ammonia

Freon-11

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

0.75

Zero

0.5

1.0

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

Wet bulb temperature

Dew point temperature

None of these

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

Heating and humidification

Cooling and dehumidification

Humidification

Dehumidification

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

Same

Higher

None of these

Lower

17. 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

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

18. Under cooling in a refrigeration cycle

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

19. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

None of these

Ammonia and hydrogen

20. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

Page 3 of 4

21. The moisture in a refrigerant is removed by

Evaporator

Driers

Dehumidifier

Safety relief valve

22. 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

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

Superheated vapour

Wet vapour

Dry saturated vapour

Saturated liquid

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

Electrically operated throttling valve

Capillary tube

Thermostatic valve

Manually operated valve

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

Less

More/less depending on size of plant

Same

26. Which of the following statement is correct?

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

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.

Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.

27. During humidification process, dry bulb temperature

Remains constant

Decreases

Increases

None of these

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

After passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

Before passing through the condenser

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

Compressor

Evaporator

Expansion valve

Condenser

30. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ min

80 kcal/ min

50 kcal/ hr

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31. An important characteristic of absorption system of refrigeration is

Very little power consumption

Quiet operation

Cooling below 0°C

Noisy operation

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

Delivery of compressor

Suction of compressor

High pressure side close to receiver

Low pressure side near receiver

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

Ammonia

All of these

CO₂

R-12

34. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

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

Remain same

Increases

Decreases

Depends on other factors

36. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

37. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

38. 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

Smaller cabinet should be used

Bigger cabinet should be used

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

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

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

Evaporator

Condenser

Compressor

Expansion valve

Refrigeration & Air-Conditioning Practice Set-1

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