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

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

2. 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

3. During sensible cooling of air ________ decreases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

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

Slightly above atmospheric pressure

24 bars

56 bars

Atmospheric pressure

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

Superheated vapour

Saturated liquid

Dry saturated vapour

Wet vapour

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

Using reagents

Sulphur sticks which on detection gives white smoke

Smelling

Halide torch which on detection produces greenish flame lighting

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

Small displacements and low condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

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

Less

Same

More/less depending on size of plant

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

Increase

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

10. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

Page 2 of 4

11. 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

12. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

13. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

14. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

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

Evaporator

Compressor

Expansion valve

Condenser

16. 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

17. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

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

Dry vapour

High pressure saturated liquid

Very wet vapour

Wet vapour

19. During dehumidification process, the relative humidity

Increases

Decreases

None of these

Remains constant

20. During humidification process, dry bulb temperature

None of these

Remains constant

Decreases

Increases

Page 3 of 4

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

Increases

Depends on other factors

Remain same

Decreases

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

Cooling and dehumidification

Dehumidification

Heating and humidification

Humidification

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

All of these

R-12

Ammonia

CO₂

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

Red

Bright green

Orange

Yellow

25. Which of the following statement is correct?

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

All of these

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.

26. 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

Degree of saturation

Relative humidity

Absolute humidity

27. The refrigerant widely used in domestic refrigerators is

R-12

Carbon dioxide

Ammonia

Sulphur dioxide

28. Which of the following statement is wrong?

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

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.

29. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Noisy operation

Quiet operation

Very little power consumption

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

Expansion valve

Evaporator

Condenser

Compressor

Page 4 of 4

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

100

Zero

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

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

33. 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

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

Suction of compressor

High pressure side close to receiver

Low pressure side near receiver

Delivery of compressor

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

1.0

0.75

0.5

Zero

37. Absorption system normally uses the following refrigerant

Freon-11

CO2

Freon-22

Ammonia

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

Higher

Lower

Same

None of these

39. During humidification process, __________ increases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

40. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Evaporator

Dehumidifier

Refrigeration & Air-Conditioning Practice Set-1

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