Refrigeration & Air-Conditioning Practice Set-1

May 16, 2021

Show paginator

Hide paginator

25%

Page 1 of 4

1. 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

2. During sensible heating of air _________ decreases.

Specific humidity

Dry bulb temperature

Wet bulb temperature

Relative humidity

3. During humidification process, __________ increases.

Dry bulb temperature

Wet bulb temperature

Relative humidity

Specific humidity

4. Under cooling in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

Increases C.O.P

C.O.P remains unaltered

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

Sulphur sticks which on detection gives white smoke

Halide torch which on detection produces greenish flame lighting

Using reagents

Smelling

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

Evaporator

Condenser

Compressor

Expansion valve

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

Increase

Decrease

Remain unaffected

May increase or decrease depending on the type of refrigerant used

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

Same

Less

More/less depending on size of plant

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

0.75

Zero

1.0

0.5

10. The fluids used in Electrolux refrigerator are

Water and hydrogen

Ammonia, water and hydrogen

Ammonia and hydrogen

None of these

Page 2 of 4

11. During humidification process, dry bulb temperature

None of these

Decreases

Remains constant

Increases

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

Ammonia

CO₂

R-12

All of these

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

Evaporator

Expansion valve

Compressor

Condenser

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

Increases

Remain same

Depends on other factors

Decreases

15. 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

16. One ton refrigeration corresponds to

50 kcal/ hr

80 kcal/ min

50 kcal/ min

80 kcal/ hr

17. 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

Humidity ratio

Relative humidity

Degree of saturation

18. During dehumidification process, the relative humidity

None of these

Decreases

Increases

Remains constant

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

Lower

Same

Higher

None of these

20. Which of the following statement is correct?

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.

In vapour absorption refrigerator, the compression of refrigerant is avoided.

Page 3 of 4

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

Dry saturated vapour

Saturated liquid

Wet vapour

Superheated vapour

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

56 bars

Atmospheric pressure

24 bars

Slightly above atmospheric pressure

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

Bright green

Red

Yellow

Orange

24. The moisture in a refrigerant is removed by

Dehumidifier

Evaporator

Driers

Safety relief valve

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

100

Zero

26. Which of the following statement is wrong?

The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.

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.

27. Absorption system normally uses the following refrigerant

CO2

Ammonia

Freon-22

Freon-11

28. Chaperon equation is a relation between

Specific volume and enthalpy

Temperature, pressure and enthalpy

Temperature, pressure, specific volume and enthalpy

Temperature and enthalpy

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

Electrically operated throttling valve

Thermostatic valve

Capillary tube

Manually operated valve

30. The refrigerant widely used in domestic refrigerators is

Sulphur dioxide

Ammonia

Carbon dioxide

R-12

Page 4 of 4

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

High pressure saturated liquid

Dry vapour

Wet vapour

Very wet vapour

32. Pick up the incorrect statement

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 used in vapour absorption cycle is non volatile

Lithium bromide plant can't operate below 0°C

33. During sensible cooling of air ________ decreases.

Dry bulb temperature

Relative humidity

Specific humidity

Wet bulb temperature

34. An important characteristic of absorption system of refrigeration is

Quiet operation

Cooling below 0°C

Very little power consumption

Noisy operation

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

After passing through the condenser

Before passing through the condenser

Before entering the expansion valve

After passing through the expansion throttle valve

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

Humidification

Dehumidification

Cooling and dehumidification

Heating and humidification

37. 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 low condensing pressures

Small displacements and high condensing pressures

38. The vapour pressure of refrigerant should be

Higher than atmospheric pressure

Equal to atmospheric pressure

Could be anything

Lower than atmospheric pressure

39. 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

Dew point temperature

Dry bulb temperature

40. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then

Perfectly tight vapour seal should be used

Bigger cabinet should be used

Smaller cabinet should be used

Refrigerant with lower evaporation temperature should be used

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