Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

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

Red

Yellow

Bright green

Orange

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

None of these

Higher

Same

Lower

3. Under cooling in a refrigeration cycle

Decreases C.O.P

C.O.P remains unaltered

Other factors decide C.O.P

Increases C.O.P

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

Evaporator

Condenser

Expansion valve

Compressor

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

Humidification

Cooling and dehumidification

Heating and humidification

Dehumidification

6. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

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

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

8. 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

None of these

Dry bulb temperature

Dew point temperature

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

0.5

Zero

0.75

1.0

10. 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

Page 2 of 4

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

Wet vapour

Dry vapour

Very wet vapour

High pressure saturated liquid

12. During humidification process, dry bulb temperature

None of these

Remains constant

Increases

Decreases

13. 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

Degree of saturation

Absolute humidity

Humidity ratio

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

Remain same

Increases

Decreases

Depends on other factors

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

Suction of compressor

High pressure side close to receiver

Delivery of compressor

Low pressure side near receiver

16. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ min

50 kcal/ min

80 kcal/ hr

17. 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 expansion throttle valve

After passing through the condenser

18. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

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

Expansion valve

Evaporator

Condenser

Compressor

20. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Quiet operation

Noisy operation

Very little power consumption

Page 3 of 4

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

More

Same

More/less depending on size of plant

Less

22. 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

Refrigerant with lower evaporation temperature should be used

Bigger cabinet should be used

Perfectly tight vapour seal should be used

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

Ammonia

CO₂

All of these

R-12

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

Sulphur sticks which on detection gives white smoke

Using reagents

Smelling

Halide torch which on detection produces greenish flame lighting

25. During sensible heating of air _________ decreases.

Dry bulb temperature

Specific humidity

Relative humidity

Wet bulb temperature

26. 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.

27. During humidification process, __________ increases.

Relative humidity

Dry bulb temperature

Wet bulb temperature

Specific humidity

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

Wet vapour

Superheated vapour

Dry saturated vapour

Saturated liquid

29. The vapour pressure of refrigerant should be

Lower than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Higher than atmospheric pressure

30. During sensible cooling of air ________ decreases.

Wet bulb temperature

Specific humidity

Dry bulb temperature

Relative humidity

Page 4 of 4

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

Atmospheric pressure

56 bars

Slightly above atmospheric pressure

24 bars

32. Absorption system normally uses the following refrigerant

Ammonia

Freon-11

CO2

Freon-22

33. The moisture in a refrigerant is removed by

Evaporator

Driers

Safety relief valve

Dehumidifier

34. 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 low condensing pressures

Large displacements and high condensing pressures

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

50

Zero

100

20

36. Pick up the incorrect statement

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

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

37. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

38. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

39. 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.

40. During dehumidification process, the relative humidity

Decreases

Remains constant

None of these

Increases

Refrigeration & Air-Conditioning Practice Set-1

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection

Refrigeration & Air-Conditioning Practice Set-1

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection