First, I DO NOT want to high jack this post. So if you want to debate the finer points of this we should start another post. Second I am a fan of aluminum radiators for reasons stated above although there is new technology on the horizon (here really just not mainstream) that could swing the performance radiator back to copper. Third for those of you that want a quick rebuttle hear it is.
I'd like to start by apologizing to you at7we2. When I said aluminum is worse than brass I went from memory and I was wrong. In my head I had brass charicteristics filed under copper. My bad.
The statement that aluminum has a supperior heat transfer coefficiant to brass is ABSOLUTELY TRUE. When I read that statement I assumed you were talking about aluminum used in radiators and also the entire radiator (copper/brass) and not just the fins.
Now to clairify what I meant above
Radiators are not built with just brass. They are copper/brass. (tube/fin)While it is true that aluminum does have a better k value than brass, the k value differential you refered to seems to be between PURE aluminum and brass. Since Aluminum radiators are not made from pure aluminum that is a useless piece of trivia. Also, as you can see below, aluminum in any form is substantialy inferior to copper and in an alloy (such as a radiator) not all that much better than brass. So, we get back to my original statement. All things being equal copper/brass radiators will out cool aluminum. Technology makes the differance. There are other things to consider as well like solder joints and tube fin heat transfer but we won't get in to that as allot of people are probably bored out of their gord by now. At the bottom is a link that does a good job of outlining some of the reasons oems have gone to aluminum in laymans terms.
Material---------------- conductivity------ density
----------------------------- W/m*K------g/cm(3)
Aluminum -------------------- 247----------2.71
Aluminum (6061)-------------- 171----------2.6-2.9
Aluminum (6063)-------------- 193----------2.6-2.9
Aluminum (7075-T6)----------- 130----------2.6-2.9
Brass (70Cu-30Zn)------------ 115----------n/a
Copper----------------------- 398----------8.94
http://www.stockcarproducts.com/rad2.htm