Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. 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

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

Ammonia

R-12

All of these

CO₂

3. Which of the following statement is wrong?

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.

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

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

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

Condenser

Evaporator

Compressor

Expansion valve

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

Depends on other factors

Remain same

Decreases

Increases

6. 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

Lithium bromide used in vapour absorption cycle is non volatile

Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

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

Suction of compressor

Delivery of compressor

Low pressure side near receiver

High pressure side close to receiver

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

More/less depending on size of plant

Less

Same

9. During sensible cooling of air ________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

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

Thermostatic valve

Manually operated valve

Capillary tube

Electrically operated throttling valve

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

100

Zero

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

Using reagents

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Smelling

13. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

14. 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

15. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

16. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

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

Heating and humidification

Dehumidification

Cooling and dehumidification

Humidification

18. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

19. During dehumidification process, the relative humidity

Decreases

None of these

Increases

Remains constant

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

Saturated liquid

Dry saturated vapour

Wet vapour

Superheated vapour

Page 3 of 4

21. 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

22. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

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

Expansion valve

Condenser

Evaporator

Compressor

24. Absorption system normally uses the following refrigerant

Ammonia

Freon-11

Freon-22

CO2

25. 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

26. During sensible heating of air _________ decreases.

Relative humidity

Dry bulb temperature

Specific humidity

Wet bulb temperature

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

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

Remain unaffected

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

56 bars

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

29. 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

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

Yellow

Bright green

Orange

Red

Page 4 of 4

31. During humidification process, __________ increases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

32. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

Water and hydrogen

None of these

Ammonia, water and hydrogen

33. 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

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

Perfectly tight vapour seal should be used

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

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

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

0.75

Zero

1.0

0.5

36. During humidification process, dry bulb temperature

Increases

Decreases

Remains constant

None of these

37. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

38. Which of the following statement is correct?

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

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.

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

39. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Very little power consumption

Quiet operation

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

Dry vapour

High pressure saturated liquid

Wet vapour

Very wet vapour

Refrigeration & Air-Conditioning Practice Set-1

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