Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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

Compressor

Expansion valve

Condenser

Evaporator

2. 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

Absolute humidity

Degree of saturation

3. 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

4. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Noisy operation

Very little power consumption

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

Slightly above atmospheric pressure

24 bars

56 bars

Atmospheric pressure

6. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

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

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Suction of compressor

8. During sensible heating of air _________ decreases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

9. 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

10. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ min

80 kcal/ hr

Page 2 of 4

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

Yellow

Bright green

Orange

Red

12. Pick up the incorrect statement

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

Lithium bromide used in vapour absorption cycle is non volatile

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

Compressor

Condenser

Expansion valve

Evaporator

14. During humidification process, dry bulb temperature

Increases

None of these

Remains constant

Decreases

15. Absorption system normally uses the following refrigerant

CO2

Freon-22

Ammonia

Freon-11

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

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

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

Wet vapour

Superheated vapour

Dry saturated vapour

Saturated liquid

18. 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

19. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Ammonia, water and hydrogen

Water and hydrogen

20. 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

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

Perfectly tight vapour seal should be used

Page 3 of 4

21. During sensible cooling of air ________ decreases.

Wet bulb temperature

Relative humidity

Specific humidity

Dry bulb temperature

22. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Higher than atmospheric pressure

23. 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.

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

R-12

All of these

CO₂

Ammonia

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

Dry bulb temperature

Wet bulb temperature

Dew point temperature

None of these

26. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

R-12

Ammonia

Carbon dioxide

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

Manually operated valve

Thermostatic valve

Electrically operated throttling valve

Capillary tube

28. 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

29. Which of the following statement is correct?

All of these

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.

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

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

Smelling

Sulphur sticks which on detection gives white smoke

Using reagents

Halide torch which on detection produces greenish flame lighting

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

Higher

Lower

Same

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

Less

Same

More/less depending on size of plant

33. 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

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

Zero

0.75

1.0

0.5

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

Increases

Depends on other factors

Decreases

Remain same

36. The reduced ambient air cooling system has

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

37. During humidification process, __________ increases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

100

Zero

39. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

40. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Dehumidifier

Evaporator

Refrigeration & Air-Conditioning Practice Set-1

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