Best ariflow direction for cooler fan?

[MichiganMat]

Hey guys-

I had some motivation this weekend and made a kickin' fan shroud for my Setrab cooler out of fiberglass. It was pretty dang fun. I mounted a big nasty fan in the shroud and Im running it on the car now. The question I have is this:

Would it be more efficient for the fan to blow outside air onto and through the cooler, or for it to suck air through the cooler and expell it as exhaust? Does anybody know? I knew I should have been an ME, a few thermo classes would do me good right about now.

m.

[Wil Ferch]

I'll take a totally educated guess at this...

-- on the one hand, with proper shrouding and ducting...you can go either way. SPAL sells both pusher and puller fans, for example.
-- on the other hand, pushing air seems more efficient since you can "compress" the air molecules ( pusher style) instead of trying to tear them apart ( puller style). In his context, Porsche'e experiments with their horizontal fan showed that is was better to push down through the finned cylinders....rather than pulling up through ( and gaining some pseudo "ground-effects"). Pulling up didn't work.
-- yet another view....the pusher will be in the immediate incoming air-stream, causing an interference with the air flow through a front mounted oil cooler. Having it "in-back", allows a cleaner shot of air, and if ducted properly, perhaps a puller is OK afterall.

When all is said and done...absent any *testing*...I'd opt for pusher.

---Wil