Free Frost Heat Excahanger Presentation Slide12

8/7/2019 Free Frost Heat Excahanger Presentation Slide12

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FREE FROST HEAT

EXCAHANGER

UNDER THE GUIDENCE OF

PROF. A .B NIDAGUNDI

PRESENTED BY

ROHIT K


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INTRODUCTIONINTRODUCTION

The California Air Resources Board enacted the

Low Emission Vehicle(LEV).

Zero Emission Vehicle (ZEV).

Pollution can cause aching lungs,wheezing,coughing and head aches.

Serious health problems.

Children is at particular risk.


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Currently, battery powered electric vehicle

is the only commercially availabletechnology that meet ZEV standards.

Slow recharge and high initial cost.

The energy storage medium may well beliquid nitrogen.

Frost free heat exchanger performance.


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CRYOGENIC AUTOMOTIVE PROPILSIONCRYOGENIC AUTOMOTIVE PROPILSION

The cryogenic automobile is a ZEV.

Operates on the thermo dynamic

potential between the ambient

atmosphere and a reservoir of liquid

nitrogen.


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The liquid nitrogen is drawn from a tank,pumped up to system pressure.

Vaporized and superheated in a heat

exchange system. High pressure and ambient temperature

gas-systems motive work.

The spent low pressure gas is exhaustedback to atmosphere.


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FROST FREE HEAT EXCHANGERFROST FREE HEAT EXCHANGER

Operate in a variety of conditions and is

structurally robust-not being hampered

by the build up of frost.

Dealing with frost formation fall into two

categories:

1) PASSIVE CONTROL.

2) ACTIVE CONTROL.


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PASSIVE CONTROLPASSIVE CONTROL

Either preventing frost formation, or over

sizing the heat exchanger such that frost

build up is unimportant.


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ADVANTAGESADVANTAGES

Mechanical simplicity.

Reliability.


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DISADVANTAGESDISADVANTAGES

In general ,less flexible in dealing with off-

design operation.


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ACTIVE CONTROLACTIVE CONTROL

Active control of frost formation entails

allowing frost to accrete and then

removing it mechanically.


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ADVANTAGESADVANTAGES

More operationally robust.

Performance of an actively controlled

heat exchanger is much less dependent

on the ambient or operational conditions

since these systems can be responsive to

different loading conditions.


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DISADVANTAGESDISADVANTAGES

Power consumption.

Poor long term reliability.


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The operating environment can be a

demanding one.

Weather conditions.

Driving conditions.

Rigorous safety.

Comfort.


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PASSIVE CONTROL METHODPASSIVE CONTROL METHOD

To prevent frost build upon sub ambient

heat exchangers, the exterior surfaces must

be kept above the freezing point of water.

The principle is the same as for multi fluid

heat exchange systems, where heat Is

transferred from source to sink via a

number of media operating in series.


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Temperature profile of frostTemperature profile of frost--free heatfree heat

exchanger element.exchanger element.

The choice of passes

was based on two

practical condition.

Passive heat exchangers

are more tightly coupled

to environmental and

operating conditions.


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ACTIVE CONTROL METHODACTIVE CONTROL METHOD

Achieve a very compact unit.

A heat exchanger has been developed

which uses rotating brushes for active frostcontrol.


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CONCLUSIONSCONCLUSIONS

The cryogenic automobile is a potential contender in theZEV market , provided certain key technologies are

demonstrated.One of these technologies is the

development of an all weather heat exchange system.A

heat exchanger that works well in a variety of operating

conditions, is structurally robust, and is not hampered bythe build up of frost is a necessary technology for the

cryogenic automobile.Experiments are yet to be

conducted to determine the actual performance.Until

road test experiments are conducted, the actual thermal

performance will not be known with enough accuracy to

support an overall recommendation for the final heat

exchange system design.


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THANK YOUTHANK YOU

Free Frost Heat Excahanger Presentation Slide12

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