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Date: Sun, 09 Mar 2008 20:16:06 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Emailing: Inclinded Radiators.doc
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Ed Anderson wrote:
> Sorry, Al, there was not any more to be had out of that document.  I can understand that all angles of inclination may not be equal - in heat transfer or drag, but must admit I was surprised to find that 55deg supposedly provided 30% more heat transfer and 20% less drag than one perpendicular to the air flow.  It would be interesting to find out the source of such a conclusion - I mean the graph looks like it comes from somewhere{:>)
>   
The last sentence is interesting, and may be the key to their finding:

Due to the use of larger radiator, weight incensement finally eliminates 
the benefits gained by an inclined radiator...

So it appears that they have a set amount of room for a radiator.  Set 
vertical, the rad is small doesn't cool well and the air is still moving 
fast so it makes a lot of drag.  Lay it over, and you increase the 
frontal area and increase radiator volume.  The air has expanded, thus 
moving slower, reducing drag.

We tend to start with a required amount of cooling, and let that lead us 
to how much radiator we need.  We design that in, whatever it takes.  
This approach starts with a given volume, and looks to fill it with the 
most cooling possible.

-- 

http://www.ronpaultimeline.com