Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. 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

Dry bulb temperature

Wet bulb temperature

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

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

Remain unaffected

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

Sulphur sticks which on detection gives white smoke

Smelling

Using reagents

Halide torch which on detection produces greenish flame lighting

4. Absorption system normally uses the following refrigerant

CO2

Ammonia

Freon-22

Freon-11

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

Bright green

Red

Yellow

Orange

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

Same

More

Less

More/less depending on size of plant

7. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ hr

50 kcal/ min

8. 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

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

Before entering the expansion valve

After passing through the condenser

Before passing through the condenser

After passing through the expansion throttle valve

10. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

Page 2 of 4

11. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

12. Pick up the incorrect statement

Lithium bromide plant can't operate below 0°C

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

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

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

100

20

50

Zero

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

Dehumidification

Heating and humidification

Cooling and dehumidification

Humidification

15. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

16. 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.

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

Depends on other factors

Remain same

Increases

Decreases

18. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

19. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

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

Ammonia

R-12

All of these

CO₂

Page 3 of 4

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

Evaporator

Condenser

Compressor

Expansion valve

22. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

23. During humidification process, __________ increases.

Relative humidity

Wet bulb temperature

Dry bulb temperature

Specific humidity

24. 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

Humidity ratio

Relative humidity

Degree of saturation

25. 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

Bigger cabinet should be used

Perfectly tight vapour seal should be used

26. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

27. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Water and hydrogen

28. Which of the following statement is correct?

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

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

Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.

29. 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

30. The moisture in a refrigerant is removed by

Driers

Evaporator

Safety relief valve

Dehumidifier

Page 4 of 4

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

None of these

Same

Lower

Higher

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

Condenser

Expansion valve

Evaporator

Compressor

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

High pressure saturated liquid

Wet vapour

Very wet vapour

Dry vapour

34. During humidification process, dry bulb temperature

Remains constant

Increases

Decreases

None of these

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

0.5

Zero

1.0

0.75

36. An important characteristic of absorption system of refrigeration is

Noisy operation

Quiet operation

Cooling below 0°C

Very little power consumption

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

Saturated liquid

Wet vapour

Superheated vapour

Dry saturated vapour

38. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Higher than atmospheric pressure

Could be anything

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

Low pressure side near receiver

Suction of compressor

Delivery of compressor

High pressure side close to receiver

40. 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

Refrigeration & Air-Conditioning Practice Set-1

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