Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Before passing through the condenser

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

2. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Driers

Evaporator

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

Evaporator

Expansion valve

Compressor

Condenser

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

Zero

100

5. 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

Relative humidity

Degree of saturation

Absolute humidity

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

Same

Less

More/less depending on size of plant

7. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

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

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

8. 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.

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

9. During humidification process, __________ increases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

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

Lower

Higher

None of these

Same

Page 2 of 4

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

Orange

Yellow

Bright green

Red

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

Decreases

Increases

Remain same

Depends on other factors

13. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

14. Absorption system normally uses the following refrigerant

Ammonia

CO2

Freon-11

Freon-22

15. During dehumidification process, the relative humidity

None of these

Increases

Remains constant

Decreases

16. During sensible heating of air _________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

17. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ hr

80 kcal/ min

18. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

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

Very wet vapour

High pressure saturated liquid

Wet vapour

Dry vapour

20. Under cooling in a refrigeration cycle

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Decreases C.O.P

Page 3 of 4

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

Capillary tube

Electrically operated throttling valve

Manually operated valve

Thermostatic valve

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

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

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

0.75

1.0

Zero

0.5

24. Which of the following statement is wrong?

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.

In vapour compression cycle, the useful part of the heat transfer is at the condenser.

25. The vapour pressure of refrigerant should be

Could be anything

Lower than atmospheric pressure

Higher than atmospheric pressure

Equal to atmospheric pressure

26. The reduced ambient air cooling system has

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

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

Compressor

Condenser

Evaporator

Expansion valve

28. 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

Dry bulb temperature

None of these

29. An important characteristic of absorption system of refrigeration is

Very little power consumption

Noisy operation

Quiet operation

Cooling below 0°C

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

Dehumidification

Cooling and dehumidification

Humidification

Heating and humidification

Page 4 of 4

31. 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

32. 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

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

Perfectly tight vapour seal should be used

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

Delivery of compressor

High pressure side close to receiver

Low pressure side near receiver

Suction of compressor

34. During humidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

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

Saturated liquid

Dry saturated vapour

Superheated vapour

Wet vapour

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

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Decrease

Increase

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

R-12

All of these

Ammonia

CO₂

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

Slightly above atmospheric pressure

56 bars

Atmospheric pressure

24 bars

39. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Water and hydrogen

Ammonia and hydrogen

40. The refrigerant widely used in domestic refrigerators is

Ammonia

Carbon dioxide

Sulphur dioxide

R-12

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