Discussion Forum

I have correctly assembled the model physics and have a working COMSOL model for the conversion of a certain species. This model does not incorporate any optimization. It is necessary to use optimization rather than a parameter swipe since there are six independent rate constants.

I built the four available demos from COMSOL regarding optimization (model library). The closest optimization example available was for 1D heat transfer into a wall (Called MATERIAL PROPERTY FITTING) in which the inner temperature was measured; similarly to my measurement of the outlet concentration from my microreactor. The experts at COMSOL used optimization to find the thermal conductivity and heat capacity of the wall material in order to match the dynamic (unsteady state) inner wall temperature which was measured. That is very similar to finding the rate constants in my 2D rectangular cross-section of the microreactor channel...

In my physical system, I vary the flow rate into the microchannel and measure the resulting change in concentration at steady state. So I have n-steady state problems for each change in the inlet velocity (flow rate). This very frequently occurs in real ChE applications...

I do not need thermal conductivity and heat capacity but rather need six rate constants to be varied during the optimization. I think I can do this (I think since I am not sure that the answer is actually right yet) for one velocity. Those rate constants will be unsatisfactory if I change the inlet velocity since with six independent variables there is a wide number of degrees of freedom for possible "physically inaccurate solutions."

A question is then:
How do I get the optimization module to understand that I have several steady state runs for which I want it to optimize the six rate constants with respect to minimums in deviation from the measured outlet concentration as a function of the inlet velocity? There must be a feature which allows this somehow in the interface? It would be labor intensive to build the optimization solver myself...I would much rather use COMSOL since I have always been very pleased with its versatility and adaptability in the past. There must be a way to fit reaction kinetics for situations outside of ideal models like CSTR, PFR and BRs...If not, a smart individual should be paid to make it and I would gladly buy it.

A second question might also be:
In the example (Called MATERIAL PROPERTY FITTING) after clicking on the optimization physics: the Global Least Squares Objective shows a file name in the blank under the label heading (experimental data) which is entitled "material_property_fitting_data.txt." How do I access that file so that I can format my outlet concentration text file correctly to put that into my optimization model.

The final question definitely is:
Why is there a (integration of the inner wall boundary)? This is under Model->Definitions. It is not used in the PDE and it is not plotted as int1 is...As far as I can deterime it does not add to the program? Should I have it in my program-if I need it and do not have it that would be humbling? I replaced it with a average function of my concentration at the outlet boundary and I wanted to compare this average at the current velocity in the simulation with the linear interpolation of my measured outlet concentration at that velocity.

Thank you for taking the time to read, assimilate and offer ideas, I appreciate it very much,