Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. 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 one heat exchanger

One cooling turbine and two heat exchangers

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

Lower

Higher

Same

None of these

3. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

4. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

5. 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

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

Depends on other factors

Increases

Remain same

Decreases

7. 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

8. During sensible cooling of air ________ decreases.

Specific humidity

Relative humidity

Dry bulb temperature

Wet bulb temperature

9. The refrigerant widely used in domestic refrigerators is

Ammonia

Carbon dioxide

Sulphur dioxide

R-12

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

None of these

Dew point temperature

Wet bulb temperature

Dry bulb temperature

Page 2 of 4

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

0.75

0.5

Zero

1.0

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

More/less depending on size of plant

More

Same

Less

13. During humidification process, __________ increases.

Specific humidity

Relative humidity

Wet bulb temperature

Dry bulb temperature

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

Compressor

Expansion valve

Evaporator

Condenser

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

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and low condensing pressures

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

Evaporator

Compressor

Expansion valve

Condenser

17. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Very little power consumption

Quiet operation

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

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Suction of compressor

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

Electrically operated throttling valve

Thermostatic valve

Capillary tube

Manually operated valve

20. 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

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21. 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

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

R-12

Ammonia

CO₂

All of these

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

100

20

50

Zero

24. 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

25. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

None of these

Water and hydrogen

Ammonia and hydrogen

26. 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 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.

27. During dehumidification process, the relative humidity

Remains constant

None of these

Increases

Decreases

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

Slightly above atmospheric pressure

24 bars

Atmospheric pressure

56 bars

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

Dry saturated vapour

Wet vapour

Saturated liquid

Superheated vapour

30. 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

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

Dehumidification

Heating and humidification

Cooling and dehumidification

Humidification

32. 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

33. Which of the following statement is correct?

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.

All of these

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

34. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

35. Absorption system normally uses the following refrigerant

Freon-11

Freon-22

CO2

Ammonia

36. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

37. During humidification process, dry bulb temperature

Increases

None of these

Remains constant

Decreases

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

Remain unaffected

Increase

Decrease

May increase or decrease depending on the type of refrigerant used

39. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Safety relief valve

Driers

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

Orange

Red

Yellow

Bright green

Refrigeration & Air-Conditioning Practice Set-1

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