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Please help! Char-o2, Char-CO2, Char-H2O reactions

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Old   May 9, 2003, 22:44
Default Please help! Char-o2, Char-CO2, Char-H2O reactions
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I meet a problem when I adopt Fluent6 and PrePDF4 to simulate coal gasifier operated at high pressure and temperature. The result indicates that there are 17%(mol) CO2+H2O at outlet however abundant char does not participate in reaction.

I want to know whether combustion model of combusting-particle in Fluent6 takes acount of Char-CO2 and Char-H2O reactions.

If Fluent6 can do, which combustion model I should select.

Otherwise, how can I do?

Please help! Any responds will be highly appreciated. Thank you.
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Old   May 10, 2003, 09:32
Default Re: Please help! Char-o2, Char-CO2, Char-H2O react
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You can with the Multiple Particle Surface Reactions model.
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Old   May 11, 2003, 22:23
Default Re: Please help! Char-o2, Char-CO2, Char-H2O react
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Dear cg or anybody,

Thanks for you help.

I use PDF+Gibb's Free Energy Minimization method to simulate reations and DPM to simulate particle motion. I define 13 species (C, C(s), CH4, CO, CO2, H, H2, H2O, N, N2, O, O2, and OH) in PrePDF4. At present, my case is similar to tut12 of Fluent6's tutorial help.

ˇ°Multiple surface reactions model is available only with the species transport model for volumetric reactions, and not with the non-premixed, premixed, or partially premixed combustion modelsˇ±(in chap19 of Fulent help, page 49). That to say I can not activate Multiple Particle Surface Reactions model in my case.

My problem is:

Whether PDF model has included C(s)-CO2 and C(s)-H2O reactions, because I have defined correlative components about these reactions?

1.If it is true, PDF model has also included C(s)-O2 reaction. I think it is not necessary to select Combustion model of combusting-particle(diffusion-limited, kinetics/diffusion limited, intrinsic-model) in Fluent6's Materials window. How do you think of it?

2.If it is wrong, maybe I must adopt UDF to define these reactions. That difficult for me, what's you advice?

Sincerely, Dai
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Old   May 15, 2003, 07:58
Default Re: Please help! Char-o2, Char-CO2, Char-H2O react
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The PDF model uses mixture fraction: you cannot have particle surface reactions since the mixture fraction assumption would be violated. UDFs won't solve this problem - you have to use multiple species.
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Old   May 28, 2003, 14:40
Default Re: Please help! Surface reaction
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hi I am new user of fluent-6. working on " flow of chemicls through soil bed involving dispersion/reactions" my problems are:

1. Representing surface reaction as oxidations of Glucose C6H12O6 + 6 O2 = 6 CO2 + 6 H2O

2. selecting appropriate preexponential factors, activation energy terms, as no exact data is available to me.

Whether I can get results with Fluent-6,or ihad to try some other option.

Anybody having some idea in respect to my doubts please reply me soon. Thanks for giving ur time. Regards, --Umesh

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