Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

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

Yellow

Orange

Bright green

Red

3. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

4. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

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

More/less depending on size of plant

Same

Less

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

Expansion valve

Compressor

Evaporator

Condenser

7. Absorption system normally uses the following refrigerant

CO2

Ammonia

Freon-22

Freon-11

8. 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.

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

Evaporator

Condenser

Compressor

Expansion valve

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

After passing through the expansion throttle valve

Before entering the expansion valve

After passing through the condenser

Before passing through the condenser

Page 2 of 4

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

Heating and humidification

Dehumidification

Humidification

Cooling and dehumidification

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

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

13. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Cooling below 0°C

Quiet operation

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

Delivery of compressor

Suction of compressor

High pressure side close to receiver

Low pressure side near receiver

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

56 bars

24 bars

Slightly above atmospheric pressure

Atmospheric pressure

16. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Lower than atmospheric pressure

Equal to atmospheric pressure

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

Same

Higher

None of these

Lower

18. During humidification process, dry bulb temperature

None of these

Increases

Decreases

Remains constant

19. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

Ammonia

R-12

20. 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

Humidity ratio

Absolute humidity

Degree of saturation

Relative humidity

Page 3 of 4

21. 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

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

22. 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

23. The fluids used in Electrolux refrigerator are

None of these

Water and hydrogen

Ammonia and hydrogen

Ammonia, water and hydrogen

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

Saturated liquid

Wet vapour

Dry saturated vapour

Superheated vapour

25. 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

26. 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 two heat exchangers

Two cooling turbines and one heat exchanger

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

Decreases

Depends on other factors

Remain same

Increases

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

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

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

Zero

100

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

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Page 4 of 4

31. Which of the following statement is wrong?

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.

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.

32. 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

33. During dehumidification process, the relative humidity

Increases

None of these

Remains constant

Decreases

34. During humidification process, __________ increases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

35. Under cooling in a refrigeration cycle

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

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

0.75

Zero

0.5

1.0

37. During sensible heating of air _________ decreases.

Wet bulb temperature

Dry bulb temperature

Specific humidity

Relative humidity

38. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Evaporator

Safety relief valve

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

CO₂

Ammonia

All of these

R-12

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

High pressure saturated liquid

Wet vapour

Very wet vapour

Dry vapour

Refrigeration & Air-Conditioning Practice Set-1

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