2 Replies Latest reply on Oct 15, 2018 2:56 AM by Tim Schäffler

    radiation issues in electronic cooling with SW flow simulation

    Tim Schäffler

      Hello together,

      first let me say sorry for my englisch. I`m a German student and I`m working on a projekt for my Thesis.

       

      The task is to simulate the thermal situation of an industrial camera with flow simulation 2018. At the moment I´m not really sure if i need radiation in my simulation. In most of the turorial they say if the temperature is not realy high I can ignore the radiation. My first simple calculation and simulations are showing someting different.

       

      The camera casing is made of anodized aluminium (silver and black). It`s size about 30x30 mm. The temperature of the camera is abaut 70 °C and 50 °C environment temperature. The power consumption is 2,5W. It`s n external study and ther`s only natural convection (and radiation).

       

      So here are my questions:

      1. Could it be possible that radiation is about 40 % of the over all heat transfer?

      2. Should I use wall or wall to ambient or for the inner part wall and the outside of the housing wall to ambient?

      3. I`m not really sure about the emissivity of my surface. the literature values have a high range between 0.5 and 0.95.

       

      Thanks a lot

       

      Greetings

        • Re: radiation issues in electronic cooling with SW flow simulation
          Mark Keown

          1 Get all your modeling sorted then add radiation the solve time with radiation will be longer.  Yes radiation can be significant some times depending on the a and e values.  Make calculations by hand to estimate where the heat is going - assume the camera is a simple cube.  You will have to calculate radiation and convection at the same time which you can not do directly.  An iterative solution is needed.  Your understanding of the problem will be far greater with preliminary calculations (don't just jump into CFD).2. Radiation to the environment should be used (and internal surface to surface) - but what is the temperature of the environment?  If this is a simulation of the camera in the real world that the surrounding environment is set ~10C less then the ambient.  In this case 40C  (use this value until you find a better one the fits your application).  If the simulation is used to compare the camera in a heat chamber then the walls of the heat chamber will be equal to the ambient air temperature.

          3. e = 0.8 until you find a better value for each surface.

          4. Natural convection.  Make sure your computational domain is large enough to capture the natural convection.  So the domain may need to be 1500 mm above and below the camera.   Experiment withe this size and increase / reduce over time to see how it affects results.  In CFD the domain foundry velocity is 0.000000  In the real world there is always some air movement from wind, hvac, movement of the object and people...  So it is not unreasonable it set some air velocity in Initial conditions (say 0.05).

          The camera is 30 x 30 x ??.  What is the other dimension?