5 Replies Latest reply on May 4, 2015 6:32 PM by David Marsden

    Heat Transfer Rates don't match in Simulation

    David Marsden

      I am trying to do a simple simulation (SWX 2015) with a 1cm cube of copper. It is plated with 100um thick (that is the thinest SWX will do) ceramic coating.   I apply 250W on the bare ceramic. I apply a convection on the bare ceramic. I run the simulation, and the temps come up.   However, when I calculate the heat transfer rates (which should be equal), I get weird results. Also I noticed that the min tamp of the copper is lower than the max temp of the ceramic (where the two are bonded).   This is my first posting here, so I do see how to post the SWX files here.

      Below are some pictures.

       

      Any insights?

       

      Thermal.JPGMin Temp Copper only.JPGMax Temp Ceramic Only.JPG

        • Re: Heat Transfer Rates don't match in Simulation
          Jared Conway

          " However, when I calculate the heat transfer rates (which should be equal), I get weird results."

           

          could you be more specific?

           

          what do you mean by calculate the heat transfer rates

           

          and what are the weird results?

           

          you can post a pack and go of your model at the top right using the "advanced editor"

           

          i'm also trying to follow your setup

           

          you applied a heat input on the bottom of your model and convection on your model as well. but no where else? IE its ok to assume everything else is insulated?

          • Re: Heat Transfer Rates don't match in Simulation
            Mike Pogue

            When I look at the plot of the AL 300 and the Cu, I see they are both 1.249e2 at the center. I'm not sure how you could get better agreement than that. The only way the min of one would correspond to the max of the other is of you are plotting through the thickness. At any rate, the AL 300 is isothermal in x and z, the difference between the max and min of it is pure noise.

             

            With respect to the heat flux, I'm going to take a stab and say you did a bulk temp of 40 C. In that case, you have:

            29426 (W/m2K)*.0001 m2*(124.9-40)K = 250 W

             

            If you have some other bulk temp, then there is some more work to do.

              • Re: Heat Transfer Rates don't match in Simulation
                David Marsden

                Thanks for the help/concern.

                The problem was that i was getting a heat flow rate on the copper of 250w (sounds good so far).

                I was getting a heat transfer rate of around 4000w, or something outrageous like that on the ceramic. (not good).

                 

                Yes Mike the bulk temp was 40 C.

                 

                For some reason I couldn't post replies here from my other computer, but I got your questions in my e-mail.

                I am back on the same computer I posted from, and now I can reply. (?)

                 

                After complaining to SWX, I finally broke out my dusty slide ruler and calculated that the delta T thru the ceramic should be roughly .01 C. Simulation said it was more like .4 C.

                 

                SWX was messing up, so I spent some time figuring out how to make the chart more precise. Then (since the ceramic is only 100 nm thick, which is the the thinnest SWX will do, I wanted 10-25 nm) I spent another day and a half getting the mesh as fine as I could along the 100 nm wall without crashing. Oh, and you can't do a 100nm mesh in SWX by the way.

                 

                Finally, I got a heat transfer rate thru the copper of 249.89C and a heat transfer rate thru the ceramic of .019C.

                 

                I called it done, and then hand calculated the derived results that I was investigating which was for a 10nm thick coating and a 25nm coating.

                 

                Anyways, with enough perseverance SWX simulation works OK within its limits.

                I just have to learn to be more patient and spend more time understanding what is going on in the simulations.

                 

                Thank you.