Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. 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

2. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

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

Compressor

Expansion valve

Condenser

Evaporator

4. 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

Degree of saturation

Relative humidity

Humidity ratio

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

Very wet vapour

Wet vapour

High pressure saturated liquid

Dry vapour

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

24 bars

Slightly above atmospheric pressure

56 bars

Atmospheric pressure

7. An important characteristic of absorption system of refrigeration is

Noisy operation

Very little power consumption

Quiet operation

Cooling below 0°C

8. During dehumidification process, the relative humidity

None of these

Increases

Remains constant

Decreases

9. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

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

Compressor

Condenser

Evaporator

Expansion valve

Page 2 of 4

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

Smelling

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Using reagents

12. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Evaporator

Safety relief valve

13. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Water and hydrogen

Ammonia, water and hydrogen

14. During humidification process, __________ increases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

15. Absorption system normally uses the following refrigerant

CO2

Freon-11

Ammonia

Freon-22

16. 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

Bigger cabinet should be used

Smaller cabinet should be used

Perfectly tight vapour seal should be used

17. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

R-12

Ammonia

Sulphur dioxide

18. During humidification process, dry bulb temperature

Decreases

Increases

None of these

Remains constant

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

Before entering the expansion valve

After passing through the condenser

Before passing through the condenser

After passing through the expansion throttle valve

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

Remain same

Increases

Decreases

Depends on other factors

Page 3 of 4

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

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

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

Cooling and dehumidification

Humidification

Dehumidification

Heating and humidification

23. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

24. Which of the following statement is wrong?

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

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

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.

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

Electrically operated throttling valve

Thermostatic valve

Capillary tube

Manually operated valve

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

Saturated liquid

Wet vapour

Dry saturated vapour

Superheated vapour

27. Pick up the incorrect statement

A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

Lithium bromide plant can't operate below 0°C

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

28. 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 one heat exchanger

Two cooling turbines and two heat exchangers

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

More/less depending on size of plant

Same

Less

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

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Page 4 of 4

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

All of these

CO₂

Ammonia

R-12

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

Higher

None of these

Same

Lower

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

Bright green

Red

Orange

Yellow

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

Zero

100

35. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Lower than atmospheric pressure

Equal to atmospheric pressure

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

0.75

Zero

0.5

1.0

37. Which of the following statement is correct?

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.

All of these

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

Suction of compressor

High pressure side close to receiver

Delivery of compressor

Low pressure side near receiver

39. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature and enthalpy

40. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ min

80 kcal/ hr

50 kcal/ hr

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Refrigeration & Air-Conditioning Practice Set-1

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