Convergence troubles with 3D heat exchanger simula
 

Hi everybody!

We are working in a 3D compact heat exchanger simulation (air - air) in Fluent. we have two rectangular ducts and between them some triangular fins. Inside rectangular ducts we set hot air (velocity, mass flow, pressure, temperature known) and over the fins flows cooling air (temperature and velocity known). We have serious converging problems, the residuals behavior is very rare. Do someone could advice us about initialization conditions and/or 3D models?

Thank you very much

Re: Convergence troubles with 3D heat exchanger si
 

set energy URF to 1 and dont reduce this. Allow explicit temperature under relaxation via TUI. Run as first order initially and cold than ramp up temperature gradually to full conditions. Ensure fins modelled as thin walls with shell conduction on and energy can get in and out of the domain ok.

Re: Convergence troubles with 3D heat exchanger si
 

Thanks for your ans,

Well, we are not experts on modeling, so we dont know how to allow explicit temperature under relaxation via TUI. We have tutorials but these dont explain how to type commands to do that you recommended us. We obtained some results changing both boundary conditions at outlet to "pressure outlet" and assuming the conditions needed but this one arent clearly and reliable. Also, we have modeled some cases modifying the viscous model options. However, we have not found any results. Do you know any case that could be modeladed accurately for this kind of heat exchanger?

Thank you so much