Nic Hume here. I'm the guy who sent in the HP-ESP128 hot-swappable PSU.
I think Dave missed the letter I sent in with the PSU. The server that this thing came out of had a series of 3x 25CFM fans just to cool the PSU (for a total of 75CFM of forced-air cooling... ) The neat thing about the fans is that they were actually stacked PAIRS of 5-blade / 3-blade fans, effectively functioning as a miniature turbine compressor to generate enough pressure to move the air through the dense components of the PSU.
Needless to say they made one hell of a racket when turned on.
As far as heat dissipation goes, I started mucking about with those PSUs to try and re-purpose them, and quickly gave up. At rest, they quickly exceeded 75deg. C while sitting on a bench. I'm terrified of what they might get up to if run under load without cooling. Regardless, they are very much NOT passively cooled !
Hope that helps fill in a few gaps!