Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

Manually operated valve

Capillary tube

Thermostatic valve

Electrically operated throttling valve

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

Before passing through the condenser

After passing through the expansion throttle valve

After passing through the condenser

Before entering the expansion valve

3. The refrigerant widely used in domestic refrigerators is

Ammonia

Carbon dioxide

Sulphur dioxide

R-12

4. 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

Humidity ratio

Degree of saturation

Relative humidity

Absolute humidity

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

Increases

Remain same

Decreases

Depends on other factors

6. The vapour pressure of refrigerant should be

Could be anything

Higher than atmospheric pressure

Equal to atmospheric pressure

Lower than atmospheric pressure

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

Small displacements and high condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

8. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

9. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

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

R-12

Ammonia

CO₂

All of these

Page 2 of 4

11. 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

Wet vapour

Dry vapour

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

0.5

Zero

0.75

1.0

13. The moisture in a refrigerant is removed by

Driers

Dehumidifier

Evaporator

Safety relief valve

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

24 bars

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

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

Less

Same

More/less depending on size of plant

More

16. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Cooling below 0°C

Noisy operation

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

20

50

100

Zero

18. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

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

Yellow

Red

Bright green

Orange

20. 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

Page 3 of 4

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

Higher

Same

None of these

Lower

22. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

23. One ton refrigeration corresponds to

50 kcal/ hr

50 kcal/ min

80 kcal/ hr

80 kcal/ min

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

High pressure side close to receiver

Delivery of compressor

Suction of compressor

Low pressure side near receiver

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

Halide torch which on detection produces greenish flame lighting

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

26. Chaperon equation is a relation between

Temperature and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

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

Cooling and dehumidification

Humidification

Dehumidification

Heating and humidification

28. 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.

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.

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

Compressor

Evaporator

Expansion valve

Condenser

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

Superheated vapour

Wet vapour

Saturated liquid

Dry saturated vapour

Page 4 of 4

31. 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

Dew point temperature

None of these

Dry bulb temperature

32. Which of the following statement is correct?

All of these

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.

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

33. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

34. Absorption system normally uses the following refrigerant

Freon-11

Freon-22

CO2

Ammonia

35. During humidification process, dry bulb temperature

Increases

Decreases

None of these

Remains constant

36. 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

Lithium bromide plant can't operate below 0°C

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

37. 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

Remain unaffected

Decrease

38. 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

39. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and two heat exchangers

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

Expansion valve

Condenser

Compressor

Evaporator

Refrigeration & Air-Conditioning Practice Set-1

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