Learning Forum

[Weiqiang Liu]

Hi all,

I have a question about how to calculate reaction enthalpy source in fluent. The reaction is:

C+O2->CO2

standard enthalpy of formation of carbon and oxygen is 0. specific heat of carbon is a constant. specific heat of oxygen and carbon dioxide is a piece wise polynomial fit of temperature. enthalpy of formation under any temperature is expressed as:

H(T)=H(0)+∫ Cp*dT

Because specific heat of oxygen and carbon dioxide is a piece wise polynomial fit of temperature. Therefore, enthalpy of formation is also a piece wise polynomial fit of temperature.

Then formation enthalpy of product minus formation enthalpy of reactants gives reaction enthalpy. Reaction enthalpy is also a piece wise temperature dependent function.

Am I doing right?

Best

Weiqiang

[DrAmine]

The enthalpy of reaction calculated by Fluent is based on formation enthalpies. Check Energy Sources Due to Reaction in Theory Guide.

I guess it is correct what you are writing. But I do not comment on user defined approaches.

[Weiqiang Liu]

Hi Amine,

Are there some macros with which I can obtain enthalpy of formation of species under any state? Or I must calculate enthalpy of formation by integration of specific heat multiplied by temperature?

Best 

Weiqiang

[DrAmine]

Not aware about that. Please have a look into the way defined the formation enthalpy and heat of reaction. You see thst no integration is done.

[Weiqiang Liu]

ok , thanks very much!