5 Replies Latest reply on Oct 22, 2015 7:14 AM by Jorge Sanchez

    Pebble Bed Heater (Heat Transfer Analysis)

    Feras Khouj

      After an unknown number of trials on thermal analysis I gave up trying and it's time to ask the experts in this field

      I have a pebble bed heater which heats the air before entering a wind tunnel.

      I'm not so familiar with the thermal analysis in computer software but I want to do it with solid works to compare the results with our results by hand calculation for our senior project.

      We have a very high temperature input in the heater but whenever I put the value I get a constant temperature all over the parts it should be gradient with the difference of the heat conductivity of the materials.

      Maybe I'm doing it wrong but I need help on how to do it correctly. We have a temperature of 1100 K and the air should reach that value within 2 hours of heating. I couldn't find a time input. I keep getting same color all over the heater and the temperature should be less than 300 K on the shell

       

      I have defined new materials in the library and I have only inserted the thermal information not all. To make sure it is correct. What inputs are required to add other than Thermal expansion coefficient, thermal conductivity and specific heat???

       

      This is a capture screen of the heater that I want to do the analysis with.

       

      screenshot heater.png

       

      Each cylinder has a different kind of material.

       

      Also I would like to know about the gap inside the cylinder if soildworks consider it as air or vacuum ?

       

      your help is appreciated

        • Re: Pebble Bed Heater (Heat Transfer Analysis)
          Jared Conway

          in thermal analysis, the software doesn't know anything about the fluid other than what you tell it by applying convection coefficients

          in a flow analysis, the air is handled through CFD

           

          this is going to be a really hard problem to solve in thermal, do you have access to flow?

           

          my suggestion for either tool is to start with a really simple example that you can validate, make it work in the software then start small with your big problem and go from there.

            • Re: Pebble Bed Heater (Heat Transfer Analysis)
              Feras Khouj

              I don't really need to do the flow analysis as the air will be stored and heated and it reaches the desire temperature 1100K then it will be released by opening the valve.

              I need to simulate the heat transfer through the parts to the shell.

               

              I hope the idea is clear to you

                • Re: Pebble Bed Heater (Heat Transfer Analysis)
                  Jared Conway

                  lets start with a really simple example

                   

                  you have a block in an air stream of 1100k

                   

                  in thermal analysis you could apply a 1100k temperature on all the faces, but the answer is simple, it will be 1100k in a steady state analysis

                   

                  in reality a better condition will be a convection coefficient based on the flow. to add accuracy, you would have different conditions on the front of the block vs top and bottom vs sides vs the back. but if the environment is 1100k and you have no heat going into the block the temperature of the block will be 1100k in a steady state analysis.

                   

                  now if you add heat to the component, the temperature will likely be different than the wall because you have a heat balance problem.

                   

                  what i'm trying to show here is the simplicity of a thermal analysis vs flow. in flow we wouldn't estimate the convection coefficient, we would let the sfotware handle that.

                   

                  now for your case, we add a shell around it. the shell and the block don't know anything about each other. but what we would do is on the inside of the shell is apply a similar convection coefficient as the walls of the block. on the outside of the shell we would apply a temperatuer that simulates the environment or a convection coefficient that simulates the environment. either way, they aren't linked and if they aren't touching, theoretically could be analyzed on their own.

                   

                  in flow, they would be linked by the air in between them.

                   

                  hopefully this helps you better understand how to get started with your analysis.

              • Re: Pebble Bed Heater (Heat Transfer Analysis)
                Jorge Sanchez

                Dear Feras:

                 

                The best way for this calculation, you need to use Ansys. Please let me know if you will need some help.

                 

                Regards

                 

                George