Mailing List flyrotary@lancaironline.net Message #57579
From: Ernest Christley <echristley@att.net>
Subject: Re: [FlyRotary] Re: Engine cooling
Date: Fri, 09 Mar 2012 11:10:50 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Tracy wrote:
Sanity check:

1) Requirement: Radiator surface required is 1.5 sq in of surface area
per cubic inch of the engine. For example: LS1 V8 Chevrolet = 350 cu in
x 1.5 = 525 sq in of radiator surface area required. For this purpose,
this applies only to the surface area of the radiator that the air flow
first makes contact with. 2) Requirement: Minimum of 3.0 cu in of cooling volume per HP produced.
For example: We only utilize up to 300 HP of an LS1 for aircraft use.
Using a dual radiator configuration with two radiators measuring 15” x
18” x 2.25” thick = the total cooling volume is 1215 cu in. Therefore, our cooling volume to HP ratio: 1215 cu in cooling volume ÷
300 HP = 4.05 cu in per HP. With this formula, we have been able to
maintain climb out temperatures of around 200°F and 190°F at cruise on
a 100°F day. With a cooling system like this, we could taxi from Houston
to Dallas with no overheating problems.

Is it just me or is the math here bogus?


He's got dual radiators that add up to 540in^2 of surface and 1215in^3 of volume.  The math is right.
What doesn't add up to me, is that he says you can get by with 3in^3/hp, but then demonstrates that 4in^3/hp is just
adequate on a reasonably hot day.  I would not take issue with the math, just his definition of what constitutes "minimum".

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