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-   -   DPM reaction (http://www.cfd-online.com/Forums/fluent/30441-dpm-reaction.html)

Alexandre October 29, 2002 04:14

DPM reaction
 
Hi,

I would like to use the DPM model to model a surface reaction but I don't want to use species. The problem is burning of solid powder.

I wrote some udfs to model the change in particle diameter, mass and the mass and energy sources.

I want to use only air and dpm (oxydizer is in the solid body). Burning of powder releases air + energy.

When I use the inert dpm model putting udf as law1 I got problems.

Anyone could help?

Jin-Wook LEE November 9, 2002 22:40

Re: DPM reaction
 
Hmmmm, it seems to be impossible to set such a problem by the current Fluent version. But many problem can be overcomed by the 'NEW IDEA' or 'REASONABLE APPROXAIMATION'. For simple example, when my friend said that it was impossible to model soild sulphar reacction by Fluent because Fluent DPM combustion model is only for coal combustion. But, as you may know, it is very simple by replacing C(s) to S(s).

Let me see.

Current DPM reaction model is based on : Solid + gas_1 --> gas_2 + Q

But you want to model : Solid + gas_1 --> gas_1 + Q

So my idea to model your problem is that set the gas_1 and gas_2 as nearly same in every aspects, including properties & molecular weight and so on. And treat gas_1 and gas_2 as different gas for the Fluent setting. But when you interprete the result, treat two species as the same one.

For example, set as,

Solid(0.01kg) + gas_1(10kg) --> gas_2(10.01kg) + Q

Molecular weight of gas_1 is 10kg/kmol, and that of gas_2 is 10.01kg/kmol. Then the behavior of gas_1 and gas_2 is nearly same. Fairly small assumption and approximation is included, but this approach might work.

Please remember that this is only my idea. I never tried this approach. But I think that 'WHY NOT ?' because 'mathematically(computational aspect) it is perfect' and 'physically it is very reasonable'.

And if you have good result by using this approach, please let me know (because I should have my patent for this idea, (joke)).

Sincerely, Jinwook


Alexandre November 12, 2002 02:48

Re: DPM reaction
 
Thanks for the answer.

It is however not applicable in my case since the ratio is very different from 0.01 / 10.

I succeed (?!?) to model something using an DPM-source UDF.

Thanks anyway.


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