5 Replies Latest reply on Dec 3, 2014 3:10 AM by Jared Conway

    Thermal Simulation, Modelling Air as a Solid?

    Philip Tsao

      Hi All,

       

      I'm fairly new to Solidworks Simulation, but I have a question that hopefully some of you may be able to help with.

       

      So in the assembly I’m trying to simulate, I have multiple blocks that are sitting on a cold plate which is kept at -2 degrees Celsius.  Some of the blocks are insulators (plastic) and some are thermally conductive (aluminum).  These blocks are mated to the cold plate through some contact resistance (which I have just estimated right now as 0.2K/W  and may not be entirely accurate). The contact between the blocks and the cold plate is just Aluminum on Aluminum with no force other than gravity.  I’ve also set all the blocks to have an initial temperature of 23C, and the cold plate to be at -2C.  I’ve added convection as well, but there is no forced air being pushed through and so I have used an estimated value for free/natural convection through air (20W/m2K).

       

      When I run the simulation, the steady state results show that the conductive blocks are at -2C and the top of the insulators are still 23C.  I would expect that the air surrounding the blocks would cool down slightly and the edges of the insulator would no longer be 23C (see picture below for a cross-section).  I’m assuming this is partly due to the way convection is modelled, as I can only specify a static bulk ambient temperature (which I set to 23C).  Obviously in reality the ambient temperature around the blocks would be changing.  I see that perhaps this type of situation is where Flow Simulation would come in handy, however, we don't have that package.

       

      Is there any way to make this simulation more accurate?  Should I model air as a solid around the blocks via conduction through air?  I realize that my convection and contact resistance numbers may not be entirely accurate right now, but regardless, I think this is a separate issue.

       

       

      test.png

        • Re: Thermal Simulation, Modelling Air as a Solid?
          Jared Conway

          are you trying to do a steady state or transient simulation?

           

          modeling air could work, but would recommend trying your approximation on a known solution before you go with it.

           

          but based on whether you want steady state or transient results, that might influence some of your setup choices and options that you have

            • Re: Thermal Simulation, Modelling Air as a Solid?
              Philip Tsao

              Hi Jared,

               

              Ideally I want to do a transient solution so I can see time dependencies.  However, in reality I would probably be ok with just seeing the end result with a steady state.

               

              I'm guessing that if I do steady state that I can estimate the final air temperature and then plug that in as my ambient bulk temperature for convection.

               

              I've currently modelled it with air as a solid and it looks more realistic now.  Any other advice?