Refrigeration & Air-Conditioning Practice Set-1

Published May 16, 2021 · Updated May 16, 2021

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1. 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

2. 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

None of these

Wet bulb temperature

3. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

4. 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

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

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

Sulphur sticks which on detection gives white smoke

6. 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.

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.

7. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

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

Yellow

Bright green

Orange

Red

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

Remain same

Increases

Depends on other factors

Decreases

10. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

CO2

Ammonia

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

Zero

100

12. The fluids used in Electrolux refrigerator are

None of these

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

13. The moisture in a refrigerant is removed by

Evaporator

Safety relief valve

Dehumidifier

Driers

14. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

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

Electrically operated throttling valve

Capillary tube

Thermostatic valve

Manually operated valve

16. 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

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

17. During sensible cooling of air ________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

18. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

19. One ton refrigeration corresponds to

80 kcal/ min

80 kcal/ hr

50 kcal/ hr

50 kcal/ min

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

Large displacements and low condensing pressures

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Small displacements and low condensing pressures

Page 3 of 4

21. During humidification process, dry bulb temperature

Increases

None of these

Decreases

Remains constant

22. 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

23. During dehumidification process, the relative humidity

Decreases

Increases

Remains constant

None of these

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

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

Expansion valve

Evaporator

Compressor

Condenser

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

0.5

Zero

0.75

1.0

27. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

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

Less

More/less depending on size of plant

Same

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

After passing through the condenser

After passing through the expansion throttle valve

Before entering the expansion valve

Before passing through the condenser

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

CO₂

R-12

All of these

Ammonia

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

24 bars

Atmospheric pressure

56 bars

Slightly above atmospheric pressure

32. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

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

Expansion valve

Compressor

Evaporator

Condenser

34. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature and enthalpy

Temperature, pressure, specific volume and enthalpy

Specific volume and enthalpy

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

Humidification

Heating and humidification

Dehumidification

Cooling and dehumidification

36. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Noisy operation

Very little power consumption

37. 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

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

Decrease

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

39. Which of the following statement is wrong?

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.

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.

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

Delivery of compressor

Low pressure side near receiver

Suction of compressor

High pressure side close to receiver

Refrigeration & Air-Conditioning Practice Set-1

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