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How To Medel Multiphase Reactors!

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Old   July 20, 2003, 04:07
Default How To Medel Multiphase Reactors!
  #1
Aqeel
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i want to model a fluidized bed reactor. it involves multiphase reacting flow i.e. gaseous reactants reacting on fluidized solid catalyst particles. The best multiphase model applicable is EULERIAN Model. But it has limitaion that species transport & reactions are not allowed. Can some body help me how to resolve this situation.
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Old   July 20, 2003, 17:17
Default Re: How To Medel Multiphase Reactors!
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ap
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I'm using the Eulerian model to simulate the fluid dynamics of fluidized beds.

However, I'm not considering heat transfer and chemical reaction.

If you use FLUENT 6.1, you can also directly model heat transfer.

If you want to model chemical reaction and species transport, you should be able to add them using user defined functions (See UDF manual).

Hi

ap
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Old   July 20, 2003, 19:55
Default Re: How To Medel Multiphase Reactors!
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Greg Perkins
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You can use Fluent 4.5 - this has more multiphase features than 6.1 - but it might be a bit slow and is being phased out as v6 gets more features.

You might like to develop your own code if you want to do this seriously, since I'm not sure how good Fluent will be, and it may be a pain to wait for them to develop parts you want.

You might also be able to use a model called MFIX which is written by the DOE and from which Fluent's Granular-Eulerian model is based.

Greg
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Old   July 24, 2003, 17:45
Default Re: How To Medel Multiphase Reactors!
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ap
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Yes. MFIX is a code for granular flows written in FORTRAN, which implements also heat transfer and chemical reaction.

You can find it for at

http://www.mfix.org

To download it you have to subscribe for free.

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ap

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Old   July 24, 2003, 19:52
Default Re: How To Medel Multiphase Reactors!
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Greg Perkins
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I don't think it would be worth using udfs here, since it would be a lot of work and if you want to do combustion, special numerical techniques are generally required to get convergence.

I have developed udf code for the full multiphase flow and reaction for FLUENT since when I started in 5.x even basic multiphase was pretty poor. But I wouldn't do this again or recommend it and it took probably around 3-6 months to get it working. If you have already developed a code it would take less but still a while I would imagine.

My guess is Fluent 6.x wil have this capability some time in the future - so I suggest to wait until then or use another code.

Greg
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Old   July 25, 2003, 17:18
Default Re: How To Medel Multiphase Reactors!
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Aqeel
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I found an article written by Fluent group where they modeled a fluidized bed with reaction. They combined Eulerian-granular multiphase model with a multispecies reacting gas phase model.

It is not mentioned how they did it or which code they used.

I contacted our fluent support regarding modeling multiphase flow with reaction and the below article. Up to now I did not receive any feed back, I do not know how it will take to get it. My next plan if no response I will contact the article authors.

The article title is Design Reactors via CFD http://www.cepmagazine.org (search it under this link)

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Old   July 27, 2003, 19:31
Default Re: How To Medel Multiphase Reactors!
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ap
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MFIX theory guide contains the model used in MFIX code to model reaction.

Implementing it in FLUENT requires time, but it should be possible.

P.S. Who are the authors of the article?

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ap
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Old   July 28, 2003, 21:00
Default Re: How To Medel Multiphase Reactors!
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Greg Perkins
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I disagree - while it may be possible in theory, I expect that it won't be worth the effort. You'll be better off getting MFIX and using that, or using Fluent 4 which can model all this with the only requirement to specify the source terms for reaction, albeit with an older code.

Before trying to implement such a complex model inside say Fluent 6, you'd be wise to remember that the release of Fluent 6 was delayed considerably and still doesn't include a treatment of reaction with the granular models. If Fluent aren't happy with their attempts (and no doubt they are working on this), then I think its a safe bet to assume anybody else will encounter difficulties and these will be magnified by the fact you can't do some things through udfs! In the end the safe option is to use a code you can control fully or at least one which is proven.

Greg

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Old   July 29, 2003, 18:41
Default Re: How To Medel Multiphase Reactors!
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Aqeel
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The authors of the article are ANDER BAKKER, AHMAD H. HAIDARI AND ELIZABETH M. MARSHALL.

I have visted the MFIX site, it contains very usfull information. However the code is still under testing and devolopment.

I will use Fluent to model the reactor without reaction while keeping searching for the combination of the multiphase and reaction models. I think this combination still not fully addressed by CFD softwares for general case.
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Old   July 29, 2003, 18:47
Default Re: How To Medel Multiphase Reactors!
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Aqeel
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The authors of the article are ANDER BAKKER, AHMAD H. HAIDARI and ELIZABETH M. MARSHALL.

I have visited the MFIX site, it contains very useful information. However the code is still under testing and development.

I will use Fluent to model the reactor without reaction while keeping searching for the combination of the multiphase and reaction models. I think this combination still not fully addressed by CFD software for general case.

Aqeel
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Old   July 30, 2003, 01:46
Default Re: How To Medel Multiphase Reactors!
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Asfaw Gezae
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Dear Sir/Madam: My name is Asfaw Gezae. I am a graduate of Addis Ababa University with a BSc in Chemical Engineering. I am currently working at the Department of Chemical Engineering in Addis Ababa University as an Assistant Lecturer and studying my MSC in Process Engineering.

Now I am in the 3rd semester and I want to do my thesis on Modeling and simulation of multiphase Reactions in different units that is on the development, implementation and validation of computational fluid dynamics (CFD) tools for Chemical Reaction Engineering. Could you give me some information (materials)? I have read from the internet that you have done a lot on this area.

I thank you in advance for any help you might be able to Provide me.

My postal address is: Asfaw Gezae P.O.BOX 122231 Addis Ababa Ethiopia

Sincerely yours,

Asfaw Gezae

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