Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

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

Decrease

Increase

May increase or decrease depending on the type of refrigerant used

Remain unaffected

3. During humidification process, __________ increases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

4. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

R-12

Ammonia

Sulphur dioxide

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

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

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

Capillary tube

Thermostatic valve

Electrically operated throttling valve

Manually operated valve

7. During sensible cooling of air ________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

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

None of these

Lower

Higher

Same

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

Wet vapour

Very wet vapour

Dry vapour

High pressure saturated liquid

10. 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 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.

Page 2 of 4

11. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Evaporator

Driers

12. 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

Absolute humidity

Humidity ratio

Relative humidity

13. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

Lithium bromide used in vapour absorption cycle is non volatile

Concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

A separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

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

Zero

50

100

20

15. Absorption system normally uses the following refrigerant

CO2

Freon-22

Freon-11

Ammonia

16. During dehumidification process, the relative humidity

None of these

Decreases

Remains constant

Increases

17. 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

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

All of these

CO₂

Ammonia

R-12

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

Compressor

Expansion valve

Evaporator

Condenser

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

Zero

0.5

0.75

1.0

Page 3 of 4

21. The fluids used in Electrolux refrigerator are

None of these

Ammonia and hydrogen

Ammonia, water and hydrogen

Water and hydrogen

22. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

23. 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

24. 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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

25. 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

26. An important characteristic of absorption system of refrigeration is

Very little power consumption

Cooling below 0°C

Noisy operation

Quiet operation

27. The vapour pressure of refrigerant should be

Could be anything

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

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

Halide torch which on detection produces greenish flame lighting

Smelling

Using reagents

Sulphur sticks which on detection gives white smoke

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

Superheated vapour

Wet vapour

Saturated liquid

Dry saturated vapour

30. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

Page 4 of 4

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

Compressor

Condenser

Expansion valve

Evaporator

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

Cooling and dehumidification

Humidification

Dehumidification

Heating and humidification

33. During humidification process, dry bulb temperature

Decreases

Remains constant

Increases

None of these

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

Bright green

Yellow

Red

Orange

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

More/less depending on size of plant

Same

Less

More

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

Decreases

Remain same

Increases

Depends on other factors

37. During sensible heating of air _________ decreases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

38. Which of the following statement is wrong?

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.

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.

39. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

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

56 bars

Slightly above atmospheric pressure

24 bars

Atmospheric pressure

Refrigeration & Air-Conditioning Practice Set-1

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