Hi, I am trying to model and replicate a TFM of a fluidised bed as mentioned in the paper Optimization of methane catalytic decomposition in a fluidized bed reactor: A computational approach. I am trying to add the chemical reactions to the model with reaction rates. How to add the Arrhenius prefactor mentioned in Table 1 of the mentioned research article?
I have attached the setup here.
fluidised_bed_01.mfx (10.8 KB)
Thanks in advance!!
Warsea
When I load your .mfx file I see the following warning
ARRHENIUS_RRATES_FLUID must be set.
If you don’t know where a keyword is located in the GUI, you can use the “Search for keyword” feature:
which brings up the keyword browser:
Clicking “Locate control” takes you to the “Options” tab in the Chemistry pane:
Once you click “Enable Arrhenius model” and go back to “Reactions”, the relevant controls are shown:
Let us know if you have further questions.
This works perfectly. I also want to add user-defined functions for the Arrhenius rates as a function of the temperature.
I looked up in the user guide,
MFiX-User_Guide.pdf (29.9 MB) , for tutorials on the same. The tutorials demonstrate how to use UDFs in specific cases, but they don’t provide sufficient details on the structure of the Fortran UDF files themselves. For example, it’s not clear what keywords, subroutine templates, etc., are required when creating a new UDF (e.g., for defining Arrhenius rates as a function of temperature). A bit more detailed explanation of how to construct a UDF file from scratch would be very helpful.
Thanks in advance!!
The Arrhenius rates are already a function of temperature. You just need to give the related coefficients, like A and Ea. The documentation of MFiX (4.14.4. Implementation of CHEMKIN mechanism in MFiX — MFiX 25.2 documentation) gives all the details about how the reaction rates are calculated in MFiX based on the coefficients from the users.
If you want the coefficients, like A or Ea, to be a function of temperature, you do need to use UDF instead of the built-in CHEMKIN ability in MFiX. MFiX has some tutorials for reacting flows. After opening MFiX GUI, go to “New project” and choose the reacting cases, like “2DTFM silane_pyrolysis” or " 3D PIC silane pyrolysis". Those tutorials have the UDFs, usr_rates.f or usr_rates_des.f for the reactions.
