How to calculate reaction enthalpy source in fluent?

- July 11, 2019 at 8:20 pm
  
  Weiqiang Liu
  Subscriber
  
  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
- July 12, 2019 at 5:59 am
  
  Amine Ben Hadj Ali
  Ansys Employee
  
  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.
- July 12, 2019 at 2:09 pm
  
  Weiqiang Liu
  Subscriber
  
  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
- July 12, 2019 at 2:45 pm
  
  Amine Ben Hadj Ali
  Ansys Employee
  
  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.
- July 15, 2019 at 2:15 pm
  
  Weiqiang Liu
  Subscriber
  
  ok , thanks very much!