Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

2. During humidification process, dry bulb temperature

Decreases

None of these

Remains constant

Increases

3. During humidification process, __________ increases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

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

Suction of compressor

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

5. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Evaporator

Safety relief valve

6. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

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

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

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

Cooling and dehumidification

Dehumidification

Humidification

Heating and humidification

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

Condenser

Compressor

Expansion valve

Evaporator

10. 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

Absolute humidity

Degree of saturation

Relative humidity

Humidity ratio

Page 2 of 4

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

Dry saturated vapour

Wet vapour

Saturated liquid

Superheated vapour

12. Which of the following statement is wrong?

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.

In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.

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

Wet bulb temperature

Dry bulb temperature

Dew point temperature

None of these

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

Zero

100

20

50

15. 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

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

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

24 bars

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

Decreases

Remain same

Increases

Depends on other factors

18. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

None of these

Ammonia and hydrogen

19. 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

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

More/less depending on size of plant

Same

More

Less

Page 3 of 4

21. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Lower than atmospheric pressure

Could be anything

Higher than atmospheric pressure

22. 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

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

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

Compressor

Expansion valve

Condenser

Evaporator

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

Remain unaffected

Decrease

May increase or decrease depending on the type of refrigerant used

Increase

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

0.75

1.0

Zero

0.5

26. Absorption system normally uses the following refrigerant

Freon-11

Ammonia

Freon-22

CO2

27. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

R-12

Ammonia

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

R-12

All of these

CO₂

Ammonia

29. 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

30. During dehumidification process, the relative humidity

Remains constant

Increases

None of these

Decreases

Page 4 of 4

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

Bright green

Orange

Yellow

Red

32. 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

33. During sensible heating of air _________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

34. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Cooling below 0°C

Quiet operation

35. 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

36. Which of the following statement is correct?

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

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.

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

Wet vapour

Very wet vapour

High pressure saturated liquid

Dry vapour

38. One ton refrigeration corresponds to

80 kcal/ hr

50 kcal/ min

50 kcal/ hr

80 kcal/ min

39. Pick up the incorrect statement

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

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

40. 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

Refrigeration & Air-Conditioning Practice Set-1

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