[Cathar]

Yeah - I did simulate on my little proggy a stepped pyramid kinda deal for the block. i.e. imagine an Aztec pyramid shape. Not quite a sphere, but for these sorts of dimensions - close enough.

It did work out pretty well, being about 2C behind the White Water (from memory) but then again my thermal simulator is also not exactly a model of sophistication, being amateuristic at best.

Like most things I do in my life, I tend to focus around the 95-99% rule. I tried to analyse where 95% of the heat was going. i.e. as one moves vertically away from the die heat flux area, and then one attempts to draw a centered bounding shape around where 95% of the heat flux is moving through that bounding shape, the shape that I was simulating was something akin to a classic venturi funnel, where the gradient of the venturi curve is dependent upon the thermal conductivity of the metal. i.e. the bulk of the heat moves straight up for a while, really only slowly radiating out. After a vertical distance of about equal to the significant dimension of the heat source, only then did it radiate out fairly evenly as per a spherical sort of pattern.

For a point-source, indeed it is a hemi-sphere, but for a rectangular source that really is quite large in proportion to the vertical distance travelled, I don't think the model you're trying to use applies very well.

Of course, my theories/models on it could just be total crap as well....

Still - very interesting what you're doing here. Glad to see some research/innovation. It's been a while.