X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ispmxmta09-srv.alltel.net ([166.102.165.170] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1033111 for flyrotary@lancaironline.net; Mon, 13 Mar 2006 21:05:49 -0500 Received-SPF: pass receiver=logan.com; client-ip=166.102.165.170; envelope-from=montyr2157@alltel.net Received: from Thorstwin ([166.102.185.184]) by ispmxmta09-srv.alltel.net with SMTP id <20060314020457.PQAK16513.ispmxmta09-srv.alltel.net@Thorstwin> for ; Mon, 13 Mar 2006 20:04:57 -0600 Message-ID: <000501c6470b$b59e4a60$01fea8c0@Thorstwin> From: "M Roberts" To: Subject: flyrotary_Web_Archive Date: Mon, 13 Mar 2006 20:05:04 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0002_01C646D9.6ACAA1F0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0002_01C646D9.6ACAA1F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 I have never seen it verified that the radiator has greater resistance, = and if it did, wouldn't it depend on the fin density and other design = variables. You could just go with a bigger lower density radiator to = equal the pressure drop of the air-cooled engine. Keep in mind that = what moves the heat is not just deltaT, but the convection coefficient. = So if you had a higher convection coeff. due to more turbulence in the = radiator core (higher velocity) you could move the same heat with less = deltaT. I am sure that there is some combination of fin density, flow = and pressure drop where you could equal the heat transfer of the higher = deltaT case. Now you have to figure out if the internal/external drag to = do this is greater than the air cooled situation. Too many variables to = have a definitive answer. I'm guessing the real difference is weight and = complexity more than drag, except for the ultra optimized case, which = none of us has the budget to attain or even measure if we did. Monty ------=_NextPart_000_0002_01C646D9.6ACAA1F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

I = guess my point=20 was that there isn=92t enough information to draw the conclusion. = But if the=20 exits are the same, and the pressure in front of the radiator is the = same as=20 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=20 thickness, fin density, etc.

In = any case; I=20 agree with your premise =96 I have seen no data that definitively = supports the=20 conclusion of lower pressure drop for cooling the air cooled = engine. =20 Should one also infer then, that the flow rate required is also about = the same =96=20 that the higher fin temp does not give a higher delta T to the cooling=20 air?

Al

I have never = seen it verified=20 that the radiator has greater resistance, and if it did, wouldn't it = depend on=20 the fin density and other design variables. You could just go with a = bigger=20 lower density radiator to equal the pressure drop of the = air-cooled=20 engine. Keep in mind that what moves the heat is not just deltaT, = but the=20 convection coefficient. So if you had a higher convection coeff. due to = more=20 turbulence in the radiator core (higher velocity) you could move the = same heat=20 with less deltaT. I am sure that there is some combination of fin = density, flow=20 and pressure drop where you could equal the heat transfer of the higher = deltaT=20 case. Now you have to figure out if the internal/external drag to do = this is=20 greater than the air cooled situation. Too many variables to have a = definitive=20 answer. I'm guessing the real difference is weight and complexity more = than=20 drag, except for the ultra optimized case, which none of us has the = budget to=20 attain or even measure if we did.

Monty

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