Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Dehumidifier

Driers

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

Ammonia

CO₂

All of these

R-12

3. 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

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

High pressure saturated liquid

Wet vapour

Very wet vapour

Dry vapour

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

Increases

Remain same

Decreases

Depends on other factors

6. Absorption system normally uses the following refrigerant

CO2

Ammonia

Freon-22

Freon-11

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

None of these

Same

Lower

Higher

8. 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

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

Sulphur sticks which on detection gives white smoke

Smelling

Halide torch which on detection produces greenish flame lighting

Using reagents

10. During dehumidification process, the relative humidity

None of these

Remains constant

Increases

Decreases

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

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

12. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

13. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

14. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Very little power consumption

Noisy operation

15. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

Superheated vapour

Dry saturated vapour

Wet vapour

Saturated liquid

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

More/less depending on size of plant

Same

Less

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

Zero

0.5

0.75

1.0

19. 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.

20. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

Page 3 of 4

21. 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

Absolute humidity

Relative humidity

22. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

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

Electrically operated throttling valve

Manually operated valve

Thermostatic valve

Capillary tube

24. During humidification process, dry bulb temperature

None of these

Decreases

Increases

Remains constant

25. 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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

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

Evaporator

Expansion valve

Compressor

Condenser

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

Orange

Red

Bright green

Yellow

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

Decrease

May increase or decrease depending on the type of refrigerant used

Remain unaffected

Increase

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

Condenser

Compressor

Expansion valve

Evaporator

30. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

Page 4 of 4

31. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

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

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

33. 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 plant can't operate below 0°C

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

34. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Increases C.O.P

35. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

Water and hydrogen

None of these

36. Which of the following statement is wrong?

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.

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.

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

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

After passing through the condenser

38. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Zero

100

40. 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

Refrigeration & Air-Conditioning Practice Set-1

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