[Amps] Force cooled heatsink aerodynamics

[Fuqua, Bill L]

  To continue. 
The box allows the fan to build up a near uniform pressure across the ends of the
heat sinks. This forces almost uniform flow of air thru all the fins, in the center, the 
out toward the edges and in between.

________________________________________
From: Fuqua, Bill L
Sent: Wednesday, February 19, 2014 5:24 PM
To: Markku Oksanen; alan at g3xaq.net; amps at contesting.com
Subject: RE: [Amps] Force cooled heatsink aerodynamics

   Ok, take a close look at the fan.
1. There is an area in the center that produce no air. So the fins up against  that have no air flow.
2. Most of the air from the fan comes out around the blade tips. That is the fastest moving part of the blades
    and centrifugal force slings the air out in that direction as well. If you set a fan in the open you will feel the
    large quantity of air off to the side.

73
Bill wa4lav

________________________________________
From: Amps [amps-bounces at contesting.com] on behalf of Markku Oksanen [markku.a.oksanen at kolumbus.fi]
Sent: Monday, February 17, 2014 5:38 PM
To: alan at g3xaq.net; amps at contesting.com
Subject: Re: [Amps] Force cooled heatsink aerodynamics

Hi



I have one of these heatsinks that have two 120 mm side by side and it is
with the air flow chamber.

The chamber is just an empty box about the thickness of the fans, in my case
perhaps 35-40 mm.

How exactly this helps I can only intuitively imagine, I would think that
having fan blades rotating very close to a dense cooling fan grid is not the
most efficient way of pushing air through.



My project is for a pair 1200 w freescale dual fets for HF, hopefully with
some headroom for reliability.



Markku

OH2RA /OG2A /WW1C



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