Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

Show paginator

Hide paginator

25%

Page 1 of 4

1. 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

2. 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

Absolute humidity

Degree of saturation

Humidity ratio

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

Expansion valve

Compressor

Condenser

Evaporator

4. During humidification process, __________ increases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

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

Orange

Bright green

Red

Yellow

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

Halide torch which on detection produces greenish flame lighting

Using reagents

Smelling

Sulphur sticks which on detection gives white smoke

7. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

8. During dehumidification process, the relative humidity

Remains constant

Decreases

Increases

None of these

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

Electrically operated throttling valve

Thermostatic valve

Manually operated valve

Capillary tube

10. The fluids used in Electrolux refrigerator are

None of these

Ammonia, water and hydrogen

Ammonia and hydrogen

Water and hydrogen

Page 2 of 4

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

Very wet vapour

Wet vapour

High pressure saturated liquid

Dry vapour

12. 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 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.

13. 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

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

Cooling and dehumidification

Heating and humidification

Humidification

Dehumidification

15. Which of the following statement is correct?

All of these

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.

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

16. Pick up the incorrect statement

Lithium bromide used in vapour absorption cycle is non volatile

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 plant can't operate below 0°C

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

Expansion valve

Evaporator

Condenser

Compressor

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

Increases

Depends on other factors

Remain same

Decreases

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

56 bars

24 bars

Atmospheric pressure

Slightly above atmospheric pressure

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

0.75

Zero

0.5

1.0

Page 3 of 4

21. During sensible cooling of air ________ decreases.

Dry bulb temperature

Wet bulb temperature

Specific humidity

Relative humidity

22. One ton refrigeration corresponds to

50 kcal/ min

50 kcal/ hr

80 kcal/ min

80 kcal/ hr

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

Small displacements and high condensing pressures

Large displacements and high condensing pressures

Large displacements and low condensing pressures

Small displacements and low condensing pressures

24. The vapour pressure of refrigerant should be

Could be anything

Lower than atmospheric pressure

Higher than atmospheric pressure

Equal to atmospheric pressure

25. 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

Perfectly tight vapour seal should be used

Bigger cabinet should be used

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

Low pressure side near receiver

High pressure side close to receiver

Delivery of compressor

Suction of compressor

27. The moisture in a refrigerant is removed by

Evaporator

Safety relief valve

Driers

Dehumidifier

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

100

Zero

29. During sensible heating of air _________ decreases.

Dry bulb temperature

Relative humidity

Wet bulb temperature

Specific humidity

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

Same

More/less depending on size of plant

Less

Page 4 of 4

31. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Quiet operation

Very little power consumption

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

Wet vapour

Saturated liquid

Superheated vapour

Dry saturated vapour

33. The reduced ambient air cooling system has

Two cooling turbines and two heat exchangers

One cooling turbine and two heat exchangers

Two cooling turbines and one heat exchanger

One cooling turbine and one heat exchanger

34. During humidification process, dry bulb temperature

Decreases

None of these

Increases

Remains constant

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

May increase or decrease depending on the type of refrigerant used

Remain unaffected

Increase

Decrease

36. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Carbon dioxide

Sulphur dioxide

37. 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

38. 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

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

Ammonia

All of these

R-12

CO₂

40. Absorption system normally uses the following refrigerant

Freon-22

Freon-11

Ammonia

CO2

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