conceptual doubt in FLUENT-UDF
 

I have written UDF, using fluent macro, “DEFINE_ADJUST and DEFINE_SOURCEs”, (file attached). Reactions are taking place inside bottom porous layer of a furnace and combustion is happening in the top part of the furnace as shown in the figure below. Fuel mixture is used which consist of (CH4, O2, H2, H2O, CO, CO2, N2 and C2H6). The source terms are hooked in "Cell Zone Conditions" of fluent. UDMI, memories in Fluent are also allocated to store data for above terms (see code file). Define_adjust are also hooked in define-function hook. Energy, Viscous K-e model, species model (eddy dissipation) and radiation (DO)are turned on.

Combustion is happening in the furnace and co co2 and temperature are developed which are used for the reduction process to happen in the bottom porous layer and accordingly variation of co and co2 as well as temperature will come inside the furnace.

UDF-EXPLANATION

Iron oxide reductions
3Fe2O3 + CO = 2Fe3O4 + CO2
Fe3O4 + CO = 3FeO + CO2
FeO + CO = Fe + CO2

carbon gasification (HIGHLY ENDOTHERMIC)
CO2 + C = 2CO

The reduction of iron ore coal composite pellet proceeds by the formation of the intermediate oxides evolution, which includes the following steps, i.e. hematite first gets converted to the magnetite then from there to wustite and finally iron and all these reduction happens by the regeneration of CO through carbon gasification equation

First order kinetics has been used for the reduction equation. details of rate eq is given n file attached.

R=(4*phi*r^2)exp(E/RT)(CONCco-(CONCco2/T)) for iron ore reduction, where CONCco is the concentration of co etc. like wise for carbon gasification as well.

I want to know/clarify following things:-

1. Is it necessary or mandatory to activate the Volumetric Reactions within the Fluent in the presence of UDF and add these reaction mentioned above separately or just UDF will do ??

2. Will theSE Volumetric Reactions duplicate the calculations i.e. will fluent calculate heat, CO AND CO2 generation from udf and from volumetric rate for the simulation ?

3.the written udf using DEFINE_SOURCE and ADJUST -----variation is happening but must confirm it with some experts if its correct even though on temperature validation is coming with 5 % accuracy.


THANK YOU ALL FOR UR ADVISE AND HELP IN ADVANCE