Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. Chaperon equation is a relation between

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

2. During humidification process, dry bulb temperature

Decreases

Remains constant

None of these

Increases

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

Orange

Yellow

Bright green

Red

4. 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.

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.

5. 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

6. Absorption system normally uses the following refrigerant

CO2

Freon-22

Freon-11

Ammonia

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

Decreases

Remain same

Depends on other factors

Increases

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

Thermostatic valve

Manually operated valve

Electrically operated throttling valve

Capillary tube

9. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Water and hydrogen

Ammonia, water and hydrogen

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

Ammonia

CO₂

All of these

R-12

Page 2 of 4

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

Evaporator

Compressor

Expansion valve

Condenser

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

Higher

Same

None of these

Lower

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

High pressure saturated liquid

Dry vapour

Very wet vapour

Wet vapour

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

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

15. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

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

0.75

Zero

0.5

1.0

17. 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

Increase

Remain unaffected

18. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

19. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Decreases C.O.P

Increases C.O.P

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

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Page 3 of 4

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

Sulphur sticks which on detection gives white smoke

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

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

Low pressure side near receiver

High pressure side close to receiver

Suction of compressor

Delivery of compressor

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

Zero

100

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

Less

More/less depending on size of plant

Same

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

Evaporator

Compressor

Expansion valve

Condenser

26. The refrigerant widely used in domestic refrigerators is

Ammonia

Carbon dioxide

R-12

Sulphur dioxide

27. The moisture in a refrigerant is removed by

Driers

Evaporator

Safety relief valve

Dehumidifier

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

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

24 bars

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

Wet vapour

Superheated vapour

Saturated liquid

Dry saturated vapour

30. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Higher than atmospheric pressure

Could be anything

Equal to atmospheric pressure

Page 4 of 4

31. Which of the following statement is correct?

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

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.

32. During dehumidification process, the relative humidity

Increases

None of these

Decreases

Remains constant

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

Dehumidification

Heating and humidification

Humidification

Cooling and dehumidification

34. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Cooling below 0°C

Quiet operation

35. 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

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

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

37. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

38. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

80 kcal/ min

39. 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

Wet bulb temperature

Dry bulb temperature

40. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Refrigeration & Air-Conditioning Practice Set-1

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