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Questions on default Arrhenius factors

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Old   July 15, 2021, 14:50
Question Questions on default Arrhenius factors
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Dear CFD community,


I'm quite new to Ansys and was wondering if there is a database or a text file with the sources of the used pre-exponential factors that can be found in Ansys. I tried searching the theory guide, but couldn't find anything.


Another thing that boggles my mind are the units of these factors. The default Arrhenius factor changes significantly when choosing volumetric reactions (i.e. 2.239e+12 for carbon monoxide oxidation) and reactions on the particle surface (i.e. for solid coke oxidation 0.002). What kind of units am I seeing? The user manual only states that they are 'consistent units'.


Sorry in advance if these questions do not fit this forum.


Thanks!
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Old   July 20, 2021, 03:07
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Hello,


Fluent uses units of J, kmol, m, s. The units of the pre-exponential factors will depend on the number of species involved in the reaction rate equation and their reaction order. The pre-exponential factor will have the units that make the reaction rate be kmol/(m^3Ěs) in case of volumetric reactions and kmol/(m^2Ěs) if you are using surface reactions. I think that this is the meaning of 'consistent units'.


I am sorry I cannot tell anything about the text file for the pre-exponential factors you are seeking.
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Old   July 20, 2021, 09:15
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Quote:
Originally Posted by User12 View Post
Hello,


Fluent uses units of J, kmol, m, s. The units of the pre-exponential factors will depend on the number of species involved in the reaction rate equation and their reaction order. The pre-exponential factor will have the units that make the reaction rate be kmol/(m^3Ěs) in case of volumetric reactions and kmol/(m^2Ěs) if you are using surface reactions. I think that this is the meaning of 'consistent units'.


I am sorry I cannot tell anything about the text file for the pre-exponential factors you are seeking.

Thank you very much for the answer, at least the units are now clear for me. I guess I will look up the factors and see if they are quoted somewhere in literature.
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