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February 3, 2012 10:56am UTC

Manipulating heat-transfer coefficient

Hi All,

I have 3 domains, from bottom to top iron, air and glas. Iron and Glas are defined as heat transfer in solid, Air as heat transfer in fluids. Iron being heated, the heat flow to air and glas.

i want to increase the heat flux from iron to air by manipulating the heat-transfer coefficient.

the convective cooling doesnt work here, it works only at outer boundary.

thanks. happy weekend

akmal

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February 4, 2012 9:18pm UTC in response to Nagi Elabbasi

Re: Manipulating heat-transfer coefficient

Thanks for your quick answer.

The easiest thing to solve my problem is by "adjust" properties of air, but by changing it, my modell will be far than reality.

the model its about a wire (long wire, outher radius 8mm) for max 300 Ampere. no air domain are defined, but a convective cooling for horisontal cylinder is defined. To have my modell same as lab meassurement i add correction factor "ka" to the heat transfer coeficient "h". "ka" is a must because not all what happen in reality can be 100% describe in model. the correction factor are depends on wire radius. bigger radius has a bigger "ka", from 1.7 until 2.4. It means more heat are transfered to air than theoriticaly should happend.

any critics or idea to "ka"?

client want to have protection sleeve around the wire and interested on the temperatur increase that caused by protection sleeve. So i adapt my model and defined an air betwen wire and protection sleeve. here comes the problem. since i defined air, i cant apply convective cooling on the outer wire surface. i actualy looking for something on the equation that allow me to implement my "ka". so that, there are the same relation of heat amount that goes to the air. i cant find it yet.

the result, there are higher temperatur on the copper than the lab measurement (4-11 temperatur different).

any idea are welcome.

best regards
akmal

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February 6, 2012 1:04pm UTC in response to Akmal

Re: Manipulating heat-transfer coefficient

Hi All,

it solved in very elegant way.

Using Form assembly to get solid and fluid virtualy separated. the solid boundary to fliud can now be used by convective cooling include "ka".

thanks to Mr Dennis Cronbach.

regards
akmal

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February 9, 2012 10:00am UTC in response to Nagi Elabbasi

Re: Manipulating heat-transfer coefficient

Of course, to avoid that by the convective cooling, the T.ext should be taken from temperature probe at the air domain below the acyrl, not ambient temperatur.

thanks for your input.

best regards
akmal hidayat

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