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-   -   UDF for devolatilization (http://www.cfd-online.com/Forums/fluent-udf/44493-udf-devolatilization.html)

chinadai April 21, 2007 03:11

UDF for devolatilization
 
I use Fluent to simulate coal gasification. The first step, coal should discharge volatile. The volatile is thought of as a pure component in Fluent, but in fact it composes of several simple components. I want to know how to write a UDF to divide volatile into simple components? How to embed above code into UDF for devolatilization law?

chinadai April 21, 2007 15:37

Re: UDF for devolatilization
 
Please give me some advice. Thanks.

Allan Walsh April 23, 2007 13:40

Re: UDF for devolatilization
 
What we do is make an artifical species (say coal_vol) that volatizes from the coal at a rate determined separately. Then, the coal_vol is divided up into separate species (i.e. CH4, H2, H2O, CO, CO2 etc.) as determined by its own species transport equation. Theoretically, there should not be any limitation on the rate of this reaction, but sometimes for solving purposes, it is good to do so.

You can make the relative fractions of the species that make up the volatiles dependant on the coal composition, which requires calculating the molecular weight and enthalpy of formation for the coal_vol. Making the volatiles composition time dependant or temperature dependant is somewhat more complex.

Or you could just use the PDF approach.

Good luck.

chinadai April 27, 2007 04:31

Re: UDF for devolatilization
 
hello, Allan. I am writing a UDF for volatile dividing, a DEFINE_DPM_SOURCE macro used. It seems to work well. I want to know the macro that you used ?


Allan Walsh April 27, 2007 12:56

Re: UDF for devolatilization
 
We use several different macros for combustion - particle laws for drying, volatiles release, char combustion, inerts, grate combustion, etc. developed over the past 20 years starting with FLUENT V.3

For the volatiles, we had thought about using the DEFINE_DPM_SOURCE macro but when we first started implementing the code, we just directly added the volatiles released (at each time step) to the C_STORAGE_R(c,t,vol_species) variable. Seemed to work ok. We have seen lots of discussion about source terms and source term linearization, which seems to be the intent of DEFINE_DPM_SOURCE macro. I guess there are different ways to get to the same endpoint.

onlylno July 1, 2013 08:30

Quote:

Originally Posted by chinadai
;141069
hello, Allan. I am writing a UDF for volatile dividing, a DEFINE_DPM_SOURCE macro used. It seems to work well. I want to know the macro that you used ?


Could you share some examples about the UDF devolatilization?
THX yujie_upc@126.com

onlylno July 1, 2013 08:32

Quote:

Originally Posted by Allan Walsh
;141084
We use several different macros for combustion - particle laws for drying, volatiles release, char combustion, inerts, grate combustion, etc. developed over the past 20 years starting with FLUENT V.3

For the volatiles, we had thought about using the DEFINE_DPM_SOURCE macro but when we first started implementing the code, we just directly added the volatiles released (at each time step) to the C_STORAGE_R(c,t,vol_species) variable. Seemed to work ok. We have seen lots of discussion about source terms and source term linearization, which seems to be the intent of DEFINE_DPM_SOURCE macro. I guess there are different ways to get to the same endpoint.



Could you give us some suggestion about the UDF devolatilization?
THX yujie_upc@126.com

onlylno July 1, 2013 08:42

Quote:

Originally Posted by chinadai
;141069
hello, Allan. I am writing a UDF for volatile dividing, a DEFINE_DPM_SOURCE macro used. It seems to work well. I want to know the macro that you used ?

Could you share me your UDF code?


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