# UDF for devolatilization

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 April 21, 2007, 03:11 UDF for devolatilization #1 chinadai Guest   Posts: n/a 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?

 April 21, 2007, 15:37 Re: UDF for devolatilization #2 chinadai Guest   Posts: n/a Please give me some advice. Thanks.

 April 23, 2007, 13:40 Re: UDF for devolatilization #3 Allan Walsh Guest   Posts: n/a 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.

 April 27, 2007, 04:31 Re: UDF for devolatilization #4 chinadai Guest   Posts: n/a 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 ?

 April 27, 2007, 12:56 Re: UDF for devolatilization #5 Allan Walsh Guest   Posts: n/a 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.

July 1, 2013, 08:30
#6
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jieyu
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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

July 1, 2013, 08:32
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jieyu
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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

July 1, 2013, 08:42
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jieyu
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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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