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

None of these

Dew point temperature

Wet bulb temperature

Dry bulb temperature

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

100

50

20

Zero

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

Atmospheric pressure

Slightly above atmospheric pressure

24 bars

56 bars

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

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

5. Pick up the incorrect statement

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

Lithium bromide plant can't operate below 0°C

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

0.75

Zero

1.0

0.5

7. The moisture in a refrigerant is removed by

Safety relief valve

Evaporator

Driers

Dehumidifier

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

Depends on other factors

Decreases

Increases

Remain same

9. During sensible heating of air _________ decreases.

Wet bulb temperature

Dry bulb temperature

Relative humidity

Specific humidity

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

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Page 2 of 4

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

Electrically operated throttling valve

Capillary tube

Manually operated valve

Thermostatic valve

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

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Using reagents

Smelling

13. 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

Relative humidity

Degree of saturation

Humidity ratio

Absolute humidity

14. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Quiet operation

Cooling below 0°C

15. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

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

High pressure side close to receiver

Suction of compressor

Low pressure side near receiver

Delivery of compressor

17. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

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

R-12

Ammonia

CO₂

All of these

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

Yellow

Red

Orange

Bright green

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

More

Same

Less

More/less depending on size of plant

Page 3 of 4

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

Condenser

Compressor

Evaporator

Expansion valve

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

Compressor

Expansion valve

Evaporator

Condenser

23. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Ammonia, water and hydrogen

Water and hydrogen

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

Higher

Lower

None of these

Same

25. Which of the following statement is wrong?

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.

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.

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

High pressure saturated liquid

Very wet vapour

Dry vapour

Wet vapour

27. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Ammonia

R-12

Sulphur dioxide

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

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

After passing through the condenser

29. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

30. Absorption system normally uses the following refrigerant

Ammonia

Freon-11

Freon-22

CO2

Page 4 of 4

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

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

Bigger cabinet should be used

Perfectly tight vapour seal should be used

32. During humidification process, dry bulb temperature

None of these

Increases

Decreases

Remains constant

33. Which of the following statement is correct?

In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.

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

All of these

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

34. During humidification process, __________ increases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

35. Under cooling in a refrigeration cycle

C.O.P remains unaltered

Increases C.O.P

Other factors decide C.O.P

Decreases C.O.P

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

Heating and humidification

Humidification

Dehumidification

Cooling and dehumidification

37. 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 two heat exchangers

One cooling turbine and one heat exchanger

38. Chaperon equation is a relation between

Temperature, pressure, specific volume and enthalpy

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

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

Dry saturated vapour

Superheated vapour

Wet vapour

Saturated liquid

40. During sensible cooling of air ________ decreases.

Dry bulb temperature

Specific humidity

Wet bulb temperature

Relative humidity

Refrigeration & Air-Conditioning Practice Set-1

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