> On Apr 10, 2019, at 4:42 PM, Daniel DeSantis <desan...@gmail.com> wrote: > > 1) Set a different Cp, rho, and k in just the PCM domain when the temperature > in that domain crosses over a certain melt temperature (350K). I tried an if > statement inside the solving loop and I think that has worked, based on some > print testing I did in the loop. I just wanted to get your opinion and see if > that was the right way to go. Seems reasonable, as long as you're calling `.setValue()` and not redefining Cp, rho, and k. In fact, I wouldn't use an `if`: >>> for step in range(steps): ... T.updateOld() ... eq.solve(dt=dt) ... rho.setValue(rho_melt, where=PCM & (T > 350)) > 2) I'd like to move this to cylindrical coordinates with the lengths being > radii. I'm not sure if the cylindrical grid is working though. And if it > isn't, is there a way to convert the diffusion equation into something that > would solve the problem in Cartesian? More specifically, how would you write > an appropriate equation for the heat transfer of a radial system in Cartesian > coordinates? In short, how would you write this: > <image.png> > in FiPy? The CylindricalGrids work fine, except for taking the gradient of the field, which is an unusual need. > > 3) Ideally, I would move this to a 2D system which is the most confusing to > me. In a 2D system, heat would be transmitted radially while air would be > flowing axially. The air would cool as it passes through the tube. The > diffusion term in the axial direction would be significantly lower than the > convection term. Can I use the same heat transfer equation you've suggested > slightly modified? I would guess the equation to be something like this: > > eq = TransientTerm(coeff = rho*Cp,var = T) + > PowerLawConvectionTerm(coeff=rho*Cp*v,var = T) == DiffusionTerm(coeff=k,var = > T) > > s.t. v = velocity of the air. Looks OK > I would also think that I would have to set the value of v to 0 at the wall > and beyond, which means v would be a CellVariable like rho and k. Actually, v should be a rank-1 FaceVariable. Anisotropic diffusion is supported in FiPy (see https://www.ctcms.nist.gov/fipy/examples/diffusion/generated/examples.diffusion.anisotropy.html), but are you really sure you have lower axial diffusivity? It seems to me more likely that transport is simply dominated by axial flow. > I also guess this equation would be subject to any changes that would be made > in question 2, regarding writing a cylindrical equation in a cartesian > system. What do you think? Use a CylindricalGrid and don't change the equation at all. > Again, thank you so much for your help and I hope I haven't taken up too much > of your time. Happy to help. _______________________________________________ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]

# Re: Question regarding Boundary Condition Implementation

Guyer, Jonathan E. Dr. (Fed) via fipy Thu, 11 Apr 2019 05:15:13 -0700

- Question regarding Boundary Conditio... Daniel DeSantis
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