Thank you Rob for your response, and sorry for taking long to answer back. 

I know that usually, heat of formation is a given property in fluent, though I can not find it as you can see in the following picture. 

So I don’t know where I should set the heat of formation?

And whether I need to use a UDF to calculate the heat of reaction or it is calculated automatically? (My objective is not to get the value of the heat of reaction, I only want to represent the energy conservation equation in the reactive zone correctly)