ways to calculate heat release of reaction in fluent.
I am doing a new project. it's air flows through porous soot cake and reacts with soot. The local soot concentration is treated as an UDS in fluent. The reaction is very simple as follows:
specific heat of carbon is constant and for other gas species, specific heat is temperature-dependent. I need to write UDF to define source term of enthalpy which arises because of carbon oxidation.
I have two ways to calculate reaction enthalpy.
Firstly: I would use C_H(c,t) to access enthalpy in the cell. Because enthalpy in a cell is mass-weighted, I can calculate enthalpy for oxygen and carbon dioxide. For carbon, the enthalpy is just Cp multiplied by ?T. Ultimately, heat release of the reaction is just enthalpy of the product minus enthalpy of reactants.
Secondly: Because I know specific heat of every species in the system. I can calculate enthalpy of formation by the following equation:
?H(0)+∫Cp(t)*dt. I don't need to use C_H(c,t) macro. I just need to use C_T macro to access temperature in the cell.
I wonder which method is correct or both of them are ok?
I need to confirm this and then go further.
PS: I received very kind help on this community and finished two projects.
Thanks very much!