Fluids

Fluids

The ‘lumped-capacitance’ model of transient heat transfer

    • Keyur Kanade
      Ansys Employee
      Hello, how do I know if I can use the 'lumped-capacitance' model of transient heat transfer for a particular problem?
    • Karthik R
      Administrator

      Hello @kkanade , you can use Biot number to quickly check if the lumped-capacitance assumption is valid or not for a particular problem. Biot Number is the ratio of conduction resistance to convective resistance. It is mathematically defined as:

      Bi = h*L / k

      where,

      h = heat transfer coefficient [W/(m^2-K)]

      L = conduction length scale [m],

      k = thermal conductivity [W/(m-K)]

      For Smaller values of Biot number the heat conduction inside the body is faster than the heat convection at its outer surfaces, and therefore the temperature gradients inside the body can be neglected. Bi in the range of <0.1 typically leads to an error of <5% if lumped-capacitance model is used.


    • Keyur Kanade
      Ansys Employee
      Hi @Kremella
      thank you for the response. I really appreciate it. 
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