Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

Show paginator

Hide paginator

25%

Page 1 of 4

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

0.5

Zero

1.0

0.75

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

Large displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Small displacements and low condensing pressures

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

Increases

Decreases

Depends on other factors

Remain same

4. The vapour pressure of refrigerant should be

Equal to atmospheric pressure

Higher than atmospheric pressure

Lower than atmospheric pressure

Could be anything

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

None of these

Same

Higher

Lower

6. 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

7. The refrigerant widely used in domestic refrigerators is

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

8. 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

Bigger cabinet should be used

Perfectly tight vapour seal should be used

Refrigerant with lower evaporation temperature should be used

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

Manually operated valve

Capillary tube

Electrically operated throttling valve

Thermostatic valve

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

Expansion valve

Condenser

Evaporator

Compressor

Page 2 of 4

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

Atmospheric pressure

24 bars

Slightly above atmospheric pressure

56 bars

12. During humidification process, __________ increases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

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

Same

Less

More/less depending on size of plant

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

Dew point temperature

None of these

Dry bulb temperature

Wet bulb temperature

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

Dehumidification

Cooling and dehumidification

Humidification

Heating and humidification

16. 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

17. 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

18. An important characteristic of absorption system of refrigeration is

Noisy operation

Cooling below 0°C

Very little power consumption

Quiet operation

19. 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

Absolute humidity

Relative humidity

Humidity ratio

Degree of saturation

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

Compressor

Evaporator

Expansion valve

Condenser

Page 3 of 4

21. During sensible heating of air _________ decreases.

Wet bulb temperature

Specific humidity

Relative humidity

Dry bulb temperature

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

All of these

R-12

CO₂

Ammonia

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

Wet vapour

Dry saturated vapour

Superheated vapour

Saturated liquid

24. Absorption system normally uses the following refrigerant

Ammonia

Freon-22

Freon-11

CO2

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

Dry vapour

Wet vapour

Very wet vapour

High pressure saturated liquid

26. During humidification process, dry bulb temperature

Increases

None of these

Decreases

Remains constant

27. 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

28. The reduced ambient air cooling system has

One cooling turbine and two heat exchangers

Two cooling turbines and two heat exchangers

One cooling turbine and one heat exchanger

Two cooling turbines and one heat exchanger

29. The moisture in a refrigerant is removed by

Driers

Safety relief valve

Dehumidifier

Evaporator

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

Orange

Bright green

Red

Yellow

Page 4 of 4

31. Under cooling in a refrigeration cycle

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

32. One ton refrigeration corresponds to

50 kcal/ hr

50 kcal/ min

80 kcal/ min

80 kcal/ hr

33. During dehumidification process, the relative humidity

Decreases

Remains constant

Increases

None of these

34. 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 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.

35. The fluids used in Electrolux refrigerator are

Ammonia and hydrogen

None of these

Water and hydrogen

Ammonia, water and hydrogen

36. During sensible cooling of air ________ decreases.

Relative humidity

Wet bulb temperature

Specific humidity

Dry bulb temperature

37. Chaperon equation is a relation between

Temperature and enthalpy

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

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

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Increase

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

100

Zero

40. Which of the following statement is correct?

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.

All of these

Refrigeration & Air-Conditioning Practice Set-1

Related

1 Response

Leave a ReplyCancel reply

Secured Payments

Protection

Refrigeration & Air-Conditioning Practice Set-1

Share this Now with Friends:

Related

1 Response

Leave a ReplyCancel reply

Secured Payments

Protection