I went geeking out and found this;
http://sci.tech-archive.net/Archive/...4-07/0547.html
From the post;
Well, this should be a doozy of a first post. I know from research
that the following combination of chemicals help reduce the surface
tension of various liquids, including water and engine coolant, to
help them transfer heat out of a radiator more effectively.
Di-Isopropyl alcohol ether
Tri-Isopropyl alcohol di-ether
Sodium molybdate
Tolytriazole
Poly Siloxane Polymer
<snip>
Answer;
By reducing surface tension you are allowing the fluid to wet the surfaces
of the pipe better, thus coming in more intimate contact with the walls.
The better the contact, the better the heat transfer. It also would allow
bubbles to move away from the wall more quickly also, thus keeping a fresh
liquid there.
<snip>