Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. One ton refrigeration corresponds to

80 kcal/ min

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

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

Capillary tube

Manually operated valve

Thermostatic valve

Electrically operated throttling valve

3. 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

Relative humidity

Humidity ratio

Absolute humidity

4. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

None of these

Ammonia and hydrogen

5. During dehumidification process, the relative humidity

Decreases

Increases

None of these

Remains constant

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

More/less depending on size of plant

Same

Less

7. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Driers

Safety relief valve

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

Ammonia

All of these

CO₂

R-12

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

Compressor

Evaporator

Condenser

Expansion valve

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

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

Delivery of compressor

Page 2 of 4

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

Superheated vapour

Wet vapour

Saturated liquid

Dry saturated vapour

12. 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 used in vapour absorption cycle is non volatile

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

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

Remain same

Increases

Decreases

Depends on other factors

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

Bright green

Yellow

Orange

Red

15. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

16. 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.

17. Absorption system normally uses the following refrigerant

CO2

Freon-22

Freon-11

Ammonia

18. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

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

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

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

Zero

100

Page 3 of 4

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

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

22. Which of the following statement is wrong?

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.

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.

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

After passing through the expansion throttle valve

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

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

Atmospheric pressure

Slightly above atmospheric pressure

56 bars

24 bars

25. During sensible cooling of air ________ decreases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

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

Expansion valve

Evaporator

Condenser

Compressor

27. During humidification process, dry bulb temperature

Increases

Decreases

Remains constant

None of these

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

Same

Higher

Lower

None of these

29. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Ammonia

R-12

Sulphur dioxide

30. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Relative humidity

Wet bulb temperature

Page 4 of 4

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

1.0

Zero

0.5

0.75

32. Chaperon equation is a relation between

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

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

Dry bulb temperature

Wet bulb temperature

None of these

Dew point temperature

34. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

35. An important characteristic of absorption system of refrigeration is

Very little power consumption

Quiet operation

Cooling below 0°C

Noisy operation

36. 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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

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

Cooling and dehumidification

Humidification

Heating and humidification

Dehumidification

38. During humidification process, __________ increases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

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

Increase

Remain unaffected

Decrease

May increase or decrease depending on the type of refrigerant used

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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