Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. 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

2. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

CO2

Ammonia

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

Red

Yellow

Bright green

Orange

4. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Water and hydrogen

None of these

Ammonia and hydrogen

5. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

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

Cooling and dehumidification

Heating and humidification

Humidification

Dehumidification

7. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

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

Expansion valve

Evaporator

Condenser

Compressor

9. An important characteristic of absorption system of refrigeration is

Quiet operation

Noisy operation

Cooling below 0°C

Very little power consumption

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

Increase

Remain unaffected

Decrease

May increase or decrease depending on the type of refrigerant used

Page 2 of 4

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

R-12

All of these

Ammonia

CO₂

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

Thermostatic valve

Capillary tube

Electrically operated throttling valve

Manually operated valve

13. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

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 plant can't operate below 0°C

14. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

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

Lower

None of these

Same

Higher

16. 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 absorption refrigerator, the compression of refrigerant is avoided.

In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.

17. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

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

Before passing through the condenser

After passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

19. During humidification process, __________ increases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

20. 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

Page 3 of 4

21. During humidification process, dry bulb temperature

Remains constant

None of these

Increases

Decreases

22. 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

Absolute humidity

Relative humidity

Humidity ratio

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

Decreases

Increases

Remain same

Depends on other factors

24. During dehumidification process, the relative humidity

Increases

Decreases

None of these

Remains constant

25. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

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

100

Zero

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

0.5

Zero

1.0

0.75

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

Wet bulb temperature

None of these

Dry bulb temperature

Dew point temperature

29. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Suction of compressor

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Page 4 of 4

31. 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

32. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

33. Which of the following statement is wrong?

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

The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.

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

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

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

Wet vapour

Dry saturated vapour

Saturated liquid

Superheated vapour

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

Less

Same

More/less depending on size of plant

36. 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

Using reagents

Smelling

37. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Driers

Dehumidifier

38. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Carbon dioxide

Sulphur dioxide

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

Expansion valve

Evaporator

Condenser

Compressor

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

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Refrigeration & Air-Conditioning Practice Set-1

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