Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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1. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

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

Compressor

Expansion valve

Evaporator

Condenser

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. Absorption system normally uses the following refrigerant

Ammonia

Freon-11

Freon-22

CO2

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

Dry saturated vapour

Saturated liquid

Wet vapour

Superheated vapour

6. During dehumidification process, the relative humidity

None of these

Increases

Decreases

Remains constant

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

100

Zero

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

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

9. 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

Dew point temperature

Wet bulb temperature

None of these

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

All of these

Ammonia

R-12

CO₂

Page 2 of 4

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

Orange

Red

Yellow

Bright green

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

Decreases

Increases

Depends on other factors

Remain same

13. The fluids used in Electrolux refrigerator are

Ammonia, water and hydrogen

Ammonia and hydrogen

Water and hydrogen

None of these

14. An important characteristic of absorption system of refrigeration is

Very little power consumption

Cooling below 0°C

Noisy operation

Quiet operation

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

Zero

0.75

0.5

1.0

16. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

17. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ hr

50 kcal/ min

80 kcal/ min

18. During sensible heating of air _________ decreases.

Relative humidity

Specific humidity

Wet bulb temperature

Dry bulb temperature

19. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

R-12

Ammonia

Sulphur dioxide

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

Bigger cabinet should be used

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Page 3 of 4

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

More/less depending on size of plant

Same

Less

22. Which of the following statement is wrong?

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.

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.

23. The moisture in a refrigerant is removed by

Dehumidifier

Safety relief valve

Evaporator

Driers

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

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

Using reagents

25. Pick up the incorrect statement

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

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

26. 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

27. Under cooling in a refrigeration cycle

Increases C.O.P

Other factors decide C.O.P

Decreases C.O.P

C.O.P remains unaltered

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

Heating and humidification

Dehumidification

Humidification

Cooling and dehumidification

29. During humidification process, dry bulb temperature

Remains constant

None of these

Decreases

Increases

30. During humidification process, __________ increases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

Page 4 of 4

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

Very wet vapour

Dry vapour

High pressure saturated liquid

Wet vapour

32. Which of the following statement is correct?

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

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

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

Evaporator

Expansion valve

Compressor

Condenser

34. 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

Degree of saturation

Relative humidity

Humidity ratio

Absolute humidity

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

High pressure side close to receiver

Suction of compressor

Delivery of compressor

Low pressure side near receiver

36. 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

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

Before passing through the condenser

Before entering the expansion valve

After passing through the condenser

After passing through the expansion throttle valve

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

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Increase

39. 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

40. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Could be anything

Equal to atmospheric pressure

Lower than atmospheric pressure

Refrigeration & Air-Conditioning Practice Set-1

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