Optimal fan adapter shape

[elmog]

What fan adapter shape minimizes backpressure and optimizes fan airflow?

I know there have been threads regarding this question. I would appreciate it very much if anyone could point me in the correct direction for research regarding this issue, I would greatly appreciate it! Thanks.

[RoadWarrior]

Me says, anything with a parabolic (or approximation thereof) cross section. Like venturi intake trumpets for increasing carburettor perfomance on old rally cars or street rods. However unless going from like 120mm to 60mm I don't think it really makes a lot of difference from one fan size to the next, especially if you're trying to do it within an inch of the fan. Pretty much anything is going to be equally as awful then :D

Someone did one with a coke bottle that looked "about right" to me, 90 to 80mm adaptor. Search coke bottle and you should find it.

Road Warrior

[elmog]

Interesting. Thanks for your help Roadwarrior.

[550M]

also, the longer it is the more effiecent. the slower the transition the better. that is until you get it long enough to have air friction to come into play :D

[elmog]

Static pressure would also build up with the longer adapter.

What if one made an adapter something like this?
+++ <Fan
\---/ <Adapter
|_|<HS

where the dashed line is the top of the HS, and the underscore is the based of the HS and the fan (represented by the pluses) would go on top of the funnel? The taper in this case is reduced, the fan is still only about an inch from the top of the HS, and the air still has room to flow out of the HS.