I'm trying to use Solidworks Simulation (2014) to calculate the radiative heat transfer between two bodies at fixed, static temperatures. Because I was getting confusing results, I set up a simple simulation consisting of two closely spaced parallel plates (1m x 1m solid bodies, 1cm separation). The upper plate is set to 300K with a temperature boundary condition, the lower set to 3K (might as well be zero), the two facing surfaces are set for surface-to-surface radiation heat transfer (closed system), and both emissivities are set to 1.
In this case, the analytical solution gives 459 W/m^2 for the heat flux between the two (infinite parallel plane) surfaces. But if I run the simulation and plot the heat flux on the facing surfaces, I get 1e-9 W/m^2 -- so either I'm setting up the problem wrong or I'm making an assumption about how Solidworks Simulation is supposed to work that is apparently not true.
If, instead of setting the upper surface to a constant temperature (300K) boundary condition, I instead apply a heat flux of 459 W/m^2 to the top of the upper surface and run the simulation, I get very close to what I expect: the upper surface comes to equilibrium at 299K and the heat flux on the upper surface is about 460 W/m^2. But I also don't quite understand why the heat flux on the lower surface that faces the warm surface is nearly zero (well, 10^-11 W/m^2). Shouldn't the heat flux leaving one surface be equal (more or less in this case due to the geometry and the nearly-unity geometric view factors) to the heat flux incident on the other? I suspect that my lack of understanding exactly what Solidworks is doing here is the root of my confusion.
Thanks in advance for any insight.