Try to simulate a case mimicking a TGA experiment, where the particle temperature increases linearly with time and also want to assign the gas temperature the same as the particle temperature, is there a easy way to do it?
For the simplifications that you want, I would suggest using an excel spreadsheet or a jupyter notebook.
If you are fine modeling the interface heat transfer, you can ramp mi temperature up linearly in time. Or any other transient function for that matter.
The ultimate goal is to check a reaction kinetic model with 737 reactions with the prescribed temperature and compare with the experimental measurements.
Ramp mi might help, but due to the endothermic reactions, the particle temperature will still vary (drop).
I imagine that the TGA experiments increased the inlet fluid temperature linearly with respect to time which, in turn, heats the particles. I question the validity of comparing simulation results to experimental data if you prescribe (i.e., overwrite) the fluid and particle temperatures. As you note, the heats of reactions for the 737 chemical reactions will cause the temperatures to evolve differently.
That said, if the temperatures are not quantities of interest and you only want the evolution of products and reactants based on a prescribed linear heating rate, then compute a reaction temperature in the UDF. This decouples the reaction rates from the computed fluid and particle temperatures.
amrex::Real const T0( 500.); // initial reaction temperature
amrex::Real const heating_rate( 1.0 ); // 1 K/sec
// Reaction temperature
amrex::Real const Trxn = T0 + reactions.time()*heating_rate;
Thanks for your suggestions!
Just did a quick search of how does the TGA get heated?
In thermogravimetric analysis (TGA), the sample is heated **using a furnace**. The sample pan, containing the material being analyzed, is placed within the furnace, which has a programmable temperature control system. The furnace heats the sample at a controlled rate, which can be adjusted depending on the specific application.
I have tried your suggestions in the simulation earlier. The case was set up according to the collaborator, it is a single sphere with 1 kg mass in a 0.68x0.68mx0.68m domain. The simulation would report unphysical value quickly. Not sure if it was caused by the endothermic reaction heat absorbed from the surrounding gas.
The way here only assigns the correct temperature to the reactions, but not the gas and solid temperature.
a 1kg particle, huh?
Yeah, 1 kg particle.