@wwenze: hope you were joking about the HDD
Tomorrow I buy the last of the supplies, and hopefully start construction. The remaining items are:
1. cute little rubber feet to screw onto the bottom of the circuit board, so that it can rest on the pot's metal bottom without shorting out. They will also be placed on the sides by epoxy or other sticking agent, to prevent shorting to the pot's sides - but I doubt there are any conductive components on the sides, and the heatsink is in the middle of the board.
2. little pointy screws to screw thru the PSU-board's existing mounting holes, and into the cute little rubber feet.
I've decided to use Duct Tape to hold the cable-bundle to the underside of my desktop, because it won't damage the desk and is easy to remove/move.
Finally, a Note about the method:
Pole Pig: Circuit in a Can of Oil
This is my inspiration! Those wonderful grey cans you see on poles by the billions, powering homes all over the world... what's inside them?
They are just steel cans, and inside is a coil immersed in mineral oil. It is passively cooled by oil convection, and is precisely the same design as my PSU-in-a-Pot project.
Passive oil-convection in a cylindrical metal case is the cheapest, most reliable electric cooling system in the world today - it is likely powering the computer you are reading this post on.
The surface area for heat transfer of the above transformer is about 5 times greater than my extra large stock pot. However, the above transformer handles at least 10,000 watts of power, and is probably rated at 15kW (likely more).
At minimum, it is moving 25 times more power than my 400W PSU at max, but has only 5 times the surface area (maybe a bit more, but not much).
Granted, the efficiency of my PSU is rated by the manufacturer at >70%, so we'll just assume 70%. The pole-pig does a bit better, probably around 95%, so at peak load waste energy is...
Pole-Pig @ 95%: 15kW: 750W
PSU @ 70%: 400W: 120W
6.25:1 waste heat (W)
5:1 surface area (approx).
So my design for the PSU-in-a-Pot is about right; it will be able to dissipate heat as well as the pole-pig can, and won't be exposed to the same temperature extremes (direct sun in particular). Remember though, my system doesn't pull 400W, and was previously running just fine on a 350. It is probably taking around 300W max, or 90W of waste energy.