How does fluent calculate the total enthalpy?
 

Does anyone know how actually fluent calculate the total enthalpy of a boundary?

I have checked the theory guide in which the total enthalpy is the sum of formation enthalpy and sensible enthalpy of all species. However, the calculation result I manually calculated is not match with the result from fluent. In my calculation, I have used piece-wise polynomial which is exactly the same as the fluent case.

I am doing combustion simulation using eddy dissipation model. The assumption of my model is ideal incompressible gas.