Refrigeration & Air-Conditioning Practice Set-1

Page 1 of 4

1. During dehumidification process, the relative humidity

Increases

None of these

Remains constant

Decreases

2. Absorption system normally uses the following refrigerant

CO2

Freon-11

Ammonia

Freon-22

3. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia and hydrogen

None of these

Ammonia, water and hydrogen

4. During humidification process, __________ increases.

Wet bulb temperature

Relative humidity

Dry bulb temperature

Specific humidity

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

Evaporator

Condenser

Expansion valve

Compressor

6. An important characteristic of absorption system of refrigeration is

Cooling below 0°C

Noisy operation

Quiet operation

Very little power consumption

7. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

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

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

8. 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.

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

Zero

0.5

1.0

0.75

10. During sensible heating of air _________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

Page 2 of 4

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

Condenser

Compressor

Evaporator

Expansion valve

12. The moisture in a refrigerant is removed by

Safety relief valve

Driers

Dehumidifier

Evaporator

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

High pressure side close to receiver

Suction of compressor

Low pressure side near receiver

Delivery of compressor

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

Ammonia

CO₂

R-12

All of these

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

Very wet vapour

Dry vapour

Wet vapour

High pressure saturated liquid

16. During humidification process, dry bulb temperature

None of these

Remains constant

Increases

Decreases

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

Yellow

Red

Orange

Bright green

18. 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

19. 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

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

Manually operated valve

Capillary tube

Thermostatic valve

Electrically operated throttling valve

Page 3 of 4

21. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

22. Which of the following statement is correct?

All of these

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

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.

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

None of these

Wet bulb temperature

Dew point temperature

Dry bulb temperature

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

More

Less

More/less depending on size of plant

Same

25. 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

Degree of saturation

Absolute humidity

Relative humidity

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

Heating and humidification

Dehumidification

Humidification

Cooling and dehumidification

27. Under cooling in a refrigeration cycle

Increases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Decreases C.O.P

28. Chaperon equation is a relation between

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

Specific volume and enthalpy

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

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

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

Decrease

May increase or decrease depending on the type of refrigerant used

Remain unaffected

Increase

Page 4 of 4

31. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ min

80 kcal/ hr

32. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and two heat exchangers

One cooling turbine and one heat exchanger

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

Higher

None of these

Lower

Same

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

After passing through the condenser

After passing through the expansion throttle valve

Before passing through the condenser

Before entering the expansion valve

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

Superheated vapour

Wet vapour

Dry saturated vapour

Saturated liquid

36. The refrigerant widely used in domestic refrigerators is

Ammonia

R-12

Carbon dioxide

Sulphur dioxide

37. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

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

50

Zero

20

100

39. 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

Refrigerant with lower evaporation temperature should be used

Smaller cabinet should be used

Perfectly tight vapour seal should be used

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

Increases

Remain same

Depends on other factors

Decreases

Refrigeration & Air-Conditioning Practice Set-1

Related

Leave a ReplyCancel reply

Secured Payments

Protection

Refrigeration & Air-Conditioning Practice Set-1

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Secured Payments

Protection