.TAeZoSysPro.HeatTransfer.Functions.Radiation.h_rad

Information

This function is used to determine the coefficient of radiative exchange when the relation which links the radiative heat flux to the difference in potential temperature is assimilated to the Newton's law of cooling as below.

Using a function to calculate h_rad rather than putting directly the relation between the heat flux and the temperature difference without function seems to us to allow a gain of stability.
Indeed, the passage by a function seemed to us to make the calculation of the exchange coefficient explicit rather than implicit.

In addition, the transition from biquadratique to a linear relationship between the heat flux and the temperature difference makes the calculation more stable numerically.

The original relation that links the radiative heat flux to the difference in potential temperature is:

Where :

• ε emissivity of the wall A
• σ is Stefan-Boltzmann's constant
• A is the surface area of the wall A
• T_A is the wall surface Temperature of the wall A
• T_B is the wall surface Temperature of the wall B

Interface

function h_rad
  input Modelica.SIunits.Temperature T_A;
  input Modelica.SIunits.Temperature T_B;
  input Real R_th "Thermal resistance between solid A and B (emissivity and view factor)";
  output Modelica.SIunits.CoefficientOfHeatTransfer h_rad;
end h_rad;