X-Virus-Scanned: clean according to Sophos on Logan.com X-PolluStop-Diagnostic: (direct reply)\eX-PolluStop-Score: 0.00\eX-PolluStop: Scanned with Niversoft PolluStop 2.1 RC1, http://www.niversoft.com/pollustop Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c4) with ESMTP id 860514 for flyrotary@lancaironline.net; Thu, 07 Apr 2005 12:44:06 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.res.rr.com [24.74.185.127]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j37GhH0W012051 for ; Thu, 7 Apr 2005 12:43:18 -0400 (EDT) Message-ID: <004801c53b90$eb0e4ec0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Radiator thickness Date: Thu, 7 Apr 2005 12:43:25 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0045_01C53B6F.63CCEC30" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0045_01C53B6F.63CCEC30 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Great chart, Al. It looks like the GM core of 3 1/2" may not be too far off optimum for = out use depending on fin density. I figured the fin density for the = cores at one point, I'll have to see what I came up with, I THINK it may = have been 14 fins/inch. The core also has "Louvers" in between the two = surfaces in that the metal of fin is punched about 7 times with a = rectangular shaped object to form a shape like a louver. I presume this = would increase the turbulence and heat exchange effectiveness - but, = might have the effect of increasing fin density factor. Ed A ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Thursday, April 07, 2005 11:40 AM Subject: [FlyRotary] Radiator thickness You can't really talk about radiator thickness without also including = the variables of the core matrix; fin density, tube spacing, = thicknesses, etc. Fin density is one of the most important. =20 The attached chart shows radiator cooling drag as a function of = thickness for some different sizes (area). Note that in this case the = curves have a minimum point, an optimum; that occurs somewhere in the = vicinity of 3" thick. Also note that it is for staggered fins at a fin = density of 8 fins/inch. Typical auto radiators, and many used in = racing, have densities of 14 - 16 fins/inch that are not staggered. = Higher fin density shifts these curves to the left, so for 14 fins/inch = (not staggered) the optimum may be more like 2 1/2" thick. For = configuration reasons, NASCAR and other racers may find that using a = thicker radiator with lower fin density is more advantageous. This may = also be true for aircraft use. IIRC, the WW II liquid cooled airplanes = had rads 6-10" thick with a rather open matrix. The chart is also for 220 kts at 15,000 ft.; a little beyond where we = generally go. However; I believe slower trades off for lower (higher = density) so the optimums MAY stay in about the same place. Anyway, the = idea is to give a feeling for how these things trade off. Putting this = together with what seems to work well is that for the automotive type = rad, somewhere around 2 =BD" thickness is good. Check the fin density = of the evaporator cores. I haven't; but I think they have a more open = core making the roughly 3" thickness more suitable. Al -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0045_01C53B6F.63CCEC30 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Great chart, Al.
 
It looks like the GM core of 3 1/2" may = not be too=20 far off optimum for out use depending on fin density.  I figured = the fin=20 density for the cores at one point, I'll have to see what I came up = with, I=20 THINK it may have been 14 fins/inch.  The core also has "Louvers" = in=20 between the two surfaces in that the metal of fin is punched about 7 = times with=20 a rectangular shaped object to form a shape like a louver.  I = presume this=20 would increase the turbulence and heat exchange effectiveness - but, = might have=20 the effect of increasing fin density factor.
 
Ed A
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Thursday, April 07, 2005 = 11:40=20 AM
Subject: [FlyRotary] Radiator=20 thickness

You can=92t really = talk about=20 radiator thickness without also including the variables of the core = matrix;=20 fin density, tube spacing, thicknesses, etc.  Fin density is one = of the=20 most important. 

 

The attached chart = shows=20 radiator cooling drag as a function of thickness for some different = sizes=20 (area).  Note that in this case the curves have a minimum point, = an=20 optimum; that occurs somewhere in the vicinity of 3=94 thick.  = Also note=20 that it is for staggered fins at a fin density of 8 fins/inch. =  Typical=20 auto radiators, and many used in racing, have densities of 14 =96 16 = fins/inch=20 that are not staggered.  Higher fin density shifts these curves = to the=20 left, so for 14 fins/inch (not staggered) the optimum may be more like = 2 1/2=94=20 thick.  For configuration reasons, NASCAR and other racers may = find that=20 using a thicker radiator with lower fin density is more = advantageous. =20 This may also be true for aircraft use.  IIRC, the WW II liquid = cooled=20 airplanes had rads 6-10=94 thick with a rather open = matrix.

 

The chart is also for = 220 kts at=20 15,000 ft.; a little beyond where we generally go.  However; I = believe=20 slower trades off for lower (higher density) so the optimums MAY stay = in about=20 the same place.  Anyway, the idea is to give a feeling for how = these=20 things trade off. Putting this together with what seems to work well = is that=20 for the automotive type rad, somewhere around 2 =BD=94 thickness is = good. =20 Check the fin density of the evaporator cores.  I haven=92t; but = I think=20 they have a more open core  making the roughly 3=94 thickness = more=20 suitable.

 

Al

 

 

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
------=_NextPart_000_0045_01C53B6F.63CCEC30--