Learning Forum

[hbachiri]

Hello, 

I am simulating a methanation reaction, where I used a UDF to calculate the reaction rate. 

In order to calculate the rate of reaction, I need first to calculate the partial pressures of different species.

Q1/ What is the total pressure ? is it C_P(c,t)? or do I need to add the operating pressure to it?

Q2/ Is there a way to take into consideration the heat of the chemical reaction (shown in equation 5.10 ), other than using UDF?

I would appreciate any help you could provide. 

Thank you 

[Rob]

I suspect C_P(c,t) is static pressure, return the value to a UDM to check. 

Re the chemical reaction, that may depend on what you're coding up. Are you using a custom reaction or sink/source terms?

[hbachiri]

Thank you Rob, yes I also think it is static pressure. 

Yes, I am using a custom reaction. I have calculated the volumetric rate using a UDF and now I would like to add the energy source term using equation 5.10

 

[Rob]

If you've set the species formation enthalpy does that do it for you? 

[hbachiri]

 

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)

 

[Rob]

I think it's the difference in the entropy: the reactants and products will sum to a different value, and the difference is heat gain/loss into the system. 

With a custom reaction the solver may do that for you. 

With source terms you need to work it out yourself. 

[hbachiri]

Thank you so much