2 Replies Latest reply on Jan 27, 2014 10:36 AM by Necmettin Kenar

    which cools faster?

    Necmettin Kenar

      hi all;
      today i tried to simulate some mechanical part's transient analysis, while doing that thing i realised that something was going wrong. to describe the problem i've prepared a summarized model.

       

      simulation:thermal (transient)
      transient total time:60sec (increment:1sec) 60 steps
      initial temp(solid model): 50 celcius

       

      convection coeff:25 W/m^2.K
      ambient temp:20 celcius

       

      i applied analysis for both aluminium(6061) and steel(st37-2) materials.

       

      when i look at the cooling curves for the same point; i realised that there is almost no differences between to simulations.

      Owing to having the same volumes; aluminium has to cool faster than steel, doesn't it? its

      there is something wrong but i couldn't find the reason yet.

      cool.JPG

       

      cooling curve for St37-2

       

      s1.JPG

      cooling curve for6061 Alloy

      s2.JPG

       

      model is also attached.

        • Re: which cools faster?
          Per Engberg

          AFAK the specific heat capacity per weight of aluminium is app. double that of steel. Since the density is app. half, similar cooling curves shoud be expected if the convection is the same.

            • Re: which cools faster?
              Necmettin Kenar

              yes Per u r right, i applied lumped capacitance method for this problem and it proved sw simulation

               

              Ekran Alıntısı.JPG

              after eliminating same values for aluminium and steel, remaining values are density and specific heat

               

              at my simulation this variables are;

               

              6061Alloy

              2700 kg/m^3 * 1300J/(kg.K) = 3510000

               

              St37-2

              7800 kg/m^3 * 440J/(kg.K) = 3432000

               

              owing to multiplications of these values are close to each other, cooling curves are also close too.