X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao02.cox.net ([68.230.241.37] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1032785 for flyrotary@lancaironline.net; Mon, 13 Mar 2006 18:04:05 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.37; envelope-from=ALVentures@cox.net Received: from BigAl ([68.7.14.39]) by fed1rmmtao02.cox.net (InterMail vM.6.01.05.02 201-2131-123-102-20050715) with ESMTP id <20060313230023.ZHFA17006.fed1rmmtao02.cox.net@BigAl> for ; Mon, 13 Mar 2006 18:00:23 -0500 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. Date: Mon, 13 Mar 2006 15:03:25 -0800 Message-ID: <000001c646f2$555d36c0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C646AF.4739F6C0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C646AF.4739F6C0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable =20 Yes, it tells you the pressure above the cooling fins of the engine = (almost full dynamic pressure). Yes I am making the assumption that the = pressure below the engine (other side of the cooling fins) is the same as the backside of the radiator. Is that not reasonable? The cooling exit is = the same in both examples. Note that the pressure above the engine was = almost full dynamic pressure WITHOUT the exit being blocked. Therefore my conclusion that the pressure differential is NOT lower on the aircooled engine. =20 Am I missing your point Al? =20 Tracy I guess my point was that there isn't enough information to draw the conclusion. But if the exits are the same, and the pressure in front of = the radiator is the same as that above the cooling fins; then the pressure = drops should be about the same. But of course it varies from one installation = to another, rad thickness, fin density, etc. =20 In any case; I agree with your premise - I have seen no data that definitively supports the conclusion of lower pressure drop for cooling = the air cooled engine. Should one also infer then, that the flow rate = required is also about the same - that the higher fin temp does not give a higher delta T to the cooling air? =20 Al =20 Al ------=_NextPart_000_0001_01C646AF.4739F6C0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

 

Yes, it tells you the pressure above the cooling fins of the engine (almost = full dynamic pressure).  Yes I am making the assumption that the = pressure below the engine (other side of the cooling fins) is the same as the backside = of the radiator.  Is that not reasonable?   The cooling = exit is the same in both examples.    Note that the pressure = above the engine was almost full dynamic pressure WITHOUT the exit being = blocked.  Therefore my conclusion that the pressure differential is NOT lower on = the aircooled engine.

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Am I missing your point Al?

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Tracy

I guess my point was that there = isn’t enough information to draw the conclusion.  But if the exits are = the same, and the pressure in front of the radiator is the same as that above the = cooling fins; then the pressure drops should be about the same.  But of = course it varies from one installation to another, rad thickness, fin density, = etc.

 

In any case; I agree with your = premise – I have seen no data that definitively supports the conclusion of lower = pressure drop for cooling the air cooled engine.  Should one also infer = then, that the flow rate required is also about the same – that the higher = fin temp does not give a higher delta T to the cooling air?

 

Al

 

Al

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