Apogee GTX

[grudgelord]

its hanging out the window to get the lowest Ambient temps :-P

I know you meant this in humor but...

I don't think placing a rad in a vacuum would work very effectively as there is no physical medium in which enable heat transfer. There might be a benefit from black-body leech but, unless I am mistaken, a rad exposed to a flow of air or water (or other thermally conductive medium) would be more efficient than exposure to mere entropy of even the coldest vacuum.

I've actually wondered about things like this in aerospace applications but naturally, not having access to a near absolute zero vacuum I haven't been able to test the notion. I don't know anyone who has access to such things either.