Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

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Page 1 of 4

1. During humidification process, dry bulb temperature

Increases

Remains constant

None of these

Decreases

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

Evaporator

Expansion valve

Condenser

Compressor

3. During sensible heating of air _________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

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

Relative humidity

Humidity ratio

Degree of saturation

Absolute humidity

5. 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

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

Decreases

Depends on other factors

Increases

Remain same

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

Small displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

8. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Smaller cabinet should be used

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Refrigerant with lower evaporation temperature should be used

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

Ammonia

CO₂

All of these

R-12

Page 2 of 4

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

Less

Same

More/less depending on size of plant

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

1.0

0.75

Zero

0.5

13. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Increases C.O.P

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

Zero

100

15. Which of the following statement is correct?

All of these

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

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.

16. During humidification process, __________ increases.

Relative humidity

Specific humidity

Dry bulb temperature

Wet bulb temperature

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

Smelling

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Using reagents

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

Dry vapour

Very wet vapour

Wet vapour

High pressure saturated liquid

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

Evaporator

Condenser

Compressor

Expansion valve

20. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

Page 3 of 4

21. The moisture in a refrigerant is removed by

Evaporator

Dehumidifier

Driers

Safety relief valve

22. 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

Dry bulb temperature

None of these

Dew point temperature

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

Low pressure side near receiver

High pressure side close to receiver

Suction of compressor

Delivery of compressor

24. The fluids used in Electrolux refrigerator are

Water and hydrogen

None of these

Ammonia, water and hydrogen

Ammonia and hydrogen

25. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

26. The refrigerant widely used in domestic refrigerators is

Carbon dioxide

Sulphur dioxide

Ammonia

R-12

27. An important characteristic of absorption system of refrigeration is

Quiet operation

Very little power consumption

Cooling below 0°C

Noisy operation

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

Yellow

Bright green

Red

Orange

29. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

Temperature and enthalpy

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

Humidification

Dehumidification

Heating and humidification

Cooling and dehumidification

Page 4 of 4

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

Slightly above atmospheric pressure

Atmospheric pressure

56 bars

24 bars

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

Thermostatic valve

Capillary tube

Manually operated valve

Electrically operated throttling valve

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

None of these

Same

Lower

Higher

34. One ton refrigeration corresponds to

80 kcal/ hr

80 kcal/ min

50 kcal/ min

50 kcal/ hr

35. During dehumidification process, the relative humidity

Decreases

None of these

Remains constant

Increases

36. Pick up the incorrect statement

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

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

37. Which of the following statement is wrong?

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.

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.

38. Absorption system normally uses the following refrigerant

CO2

Freon-22

Ammonia

Freon-11

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

Increase

Remain unaffected

Decrease

May increase or decrease depending on the type of refrigerant used

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

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