Learning Forum

[azazmce]

Hello everyone,

If only pre-exponential factor and activation energy of a reaction are provided, can the reaction and kinetics be used in ANSYS Fluent? If the corresponding temperature exponent and rate exponent are not available and not included in the Fluent, can the simulation provide acceptable results?

Note: I am using species model and volumetric reactions in Fluent

Example:

CH3OH + 1.5 O2 = CO2 + 2 H2O

(pre-exponential coefficient 1.799e+10 and activation energy value of 1.256e+8 (J/kg mole)).

A snapshot of the reactions section of Fluent is attached here.

[Rob]

Check the maths in the manual to ensure that setting the Temperature Exponent like that doesn't cause divide by zero or multiply by infinity. Given most reactions speed up when things get hot I would question the validity of your assumption.

[azazmce]

Thank you for your reply.
The rate constant of reaction using the Arrhenius expression is given below (from Fluent manual). Here if the temperature exponent is considered zero the term would be equal to 1. In that case, is it okay to not specify the value if the temperature exponent is not available in the literature for some reaction?

[Rob]

If the value isn't available is that because it's zero or because you haven't found it? If it's the former then that should be OK, if it's the latter your results could be very wrong.

[azazmce]

Thanks a lot for your reply.

[SURAJ GHIWE]

Hi 

I am doing combustion modelling of biomass combustion using the species transport model in fluent. I have used a volumetric reaction with an eddy-dissipation model. I am employing various reactions of different compositions but in each reaction, I do not have the values of the rate exponent. Where do get those values and what if we don't provide those values if not known, will it affect the results?