Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. Absorption system normally uses the following refrigerant

Freon-22

CO2

Freon-11

Ammonia

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

100

Zero

3. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

None of these

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

Lower

Same

None of these

Higher

5. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

6. An important characteristic of absorption system of refrigeration is

Noisy operation

Very little power consumption

Quiet operation

Cooling below 0°C

7. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Carbon dioxide

Sulphur dioxide

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

Same

Less

More/less depending on size of plant

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

Dew point temperature

None of these

Dry bulb temperature

Wet bulb temperature

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

Zero

0.5

1.0

0.75

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11. 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 condenser

After passing through the expansion throttle valve

12. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

13. 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

Absolute humidity

Humidity ratio

Degree of saturation

Relative humidity

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

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

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

R-12

Ammonia

All of these

CO₂

16. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

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

Halide torch which on detection produces greenish flame lighting

Smelling

Using reagents

Sulphur sticks which on detection gives white smoke

18. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Dehumidifier

Driers

19. During humidification process, dry bulb temperature

Increases

Decreases

Remains constant

None of these

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

Dry saturated vapour

Wet vapour

Superheated vapour

Saturated liquid

Page 3 of 4

21. 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

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

Expansion valve

Compressor

Condenser

Evaporator

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

Wet vapour

Very wet vapour

Dry vapour

High pressure saturated liquid

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

Bigger cabinet should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

25. 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.

26. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

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

Remain same

Decreases

Increases

Depends on other factors

28. Which of the following statement is correct?

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.

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

29. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

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

Humidification

Dehumidification

Heating and humidification

Cooling and dehumidification

Page 4 of 4

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

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

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

Capillary tube

Manually operated valve

Electrically operated throttling valve

Thermostatic valve

33. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

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

Atmospheric pressure

56 bars

Slightly above atmospheric pressure

24 bars

35. During dehumidification process, the relative humidity

Decreases

None of these

Increases

Remains constant

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

Evaporator

Compressor

Expansion valve

Condenser

37. Under cooling in a refrigeration cycle

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Decreases C.O.P

38. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

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

Bright green

Orange

Yellow

Red

40. 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

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

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