3 Replies Latest reply on May 8, 2012 9:10 AM by David Maxham

    Heat transfer (disc cooling)

    Gintautas Nesvarbu

      Hi,

       

      I hope that somebody will help me with my problem. I will try to explain as best as I can including pictures of attempt and description of the problem.

       

      I'm trying to simulate brake cooling by using forced convection. The problem is that with my conditions it doesn't show the cooling process. A temperature of 800K stays the same no matter what I try. Air temperature stays the same as well. I know heat transfer coeficient of air passing by, but I don't know where to apply it, as it only lets me to apply for solids (whole part). I know the maximum temperature that brake disc is going to reach.

       

       

       

       

       

      A complete desing looks like thatpicture.jpg

       

      My attempt to solution (I'm using only the brake disc to find a method as this saves my time) and results needed:

       

      Forced convection (cooling) in solids simulation problem:

      • Wall temperature (800K) and fluid temperature (293K) stays the same, even if cold (293K) air flow is passing through.

      Results needed and conditions:

      • Temperature change in fluid, depending on solid temperature.
      • Temperature change in solid due to cooling effect of air.
      • No fans.
      • Solid (brake disc) is rotating.

       

      1.jpg

      Steps taken, setting up in wizard:

       

      Heat conduction in solids                                                                                                                                                    

                                                                                                                                                           

                       

      2.jpg                    

        Fluid - Air

       

      3.jpg                    

       

      Solid material – gray cast iron.                                                                                

      4.jpg                                  

      Initial solid temperature – 800K, Velocity in X direction 30m/s. Temperature 293.2K.

       

      5.jpg

      Further conditions: 

       

      Boundary Condition – Real Wall temperature 800K.

      6.jpg

       

      Solid material – Grey cast iron.

       

      7.jpg


      Flow simulation type: External

       

       

      THANK YOU all in advance.

        • Re: Heat transfer (disc cooling)
          Chris Michalski

          Are you looking to see the local temperature drop (i.e. it is coldest at the air impingement point and increases as it makes it way back to that rotation?).

           

          One problem is that you modeled the rotor as a real wall 800K - that means that your rotor is always going to stay 800K.  If you want to see a temperature drop then what you'd want to do is input the heat from friction applied to the faces as a surface source.  This way as the air removes heat and the friction increases heat you will see the result of these two offsetting effects.

           

          The biggest problem is going to be that SW Flow does not do motion.  You can simulate motion with a rotating reference frame but all that does is move the fluids around the part.  Potentially modelling your cooling as just the block around the rotor and adding the air flow characteristics, then putting a rotating reference frame around the rotor so that it drags the air around as if the rotor is spinning.

           

          If you change the temperature scale when looking at the flow, is there any change in air temperature?