X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2490791 for flyrotary@lancaironline.net; Thu, 15 Nov 2007 22:27:44 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Received: from edward2 ([24.74.103.61]) by cdptpa-omta06.mail.rr.com with SMTP id <20071116032706.TCEE507.cdptpa-omta06.mail.rr.com@edward2> for ; Fri, 16 Nov 2007 03:27:06 +0000 Message-ID: <000701c82800$e2408790$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Thick vs Thin was : Diffuser Configuration Comparison Date: Thu, 15 Nov 2007 22:29:23 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0004_01C827D6.F90B2180" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0004_01C827D6.F90B2180 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ok, Dave, Just to enable you to keep your promise of not making any more = points, I will refrain from my crushing rebuttal along the lines of your = thin rad running out of mass flow before I run out of DeltaT {:>) I 'm afraid I agree with Monty's assessment of it being a sort of snipe = hunt at our level of resources and that since we are most often fitting = our cooling systems into airframes not designed for liquid cooling = everything ends up being a compromise which fortuitously works (most of = the time). I think it was a good topic and got wrung out fairly well - whichever = side of the core you are on {::>) Ed ----- Original Message -----=20 From: David Leonard=20 To: Rotary motors in aircraft=20 Sent: Thursday, November 15, 2007 10:14 PM Subject: [FlyRotary] Re: Thick vs Thin was : Diffuser Configuration = Comparison Ed Anderson Wrote: So IF in installing the thicker core, I slow down the mass flow = through the duct by 1/2 (which I can easily do - increasing it might be = more difficult) then the air velocity through the core will be reduced. = With the velocity decreased, the air will take longer to transverse the = core. The longer the air takes to move through the core the more heat = it will absorb, the more heat the air absorbs the greater the DeltaT of = the air. The greater the deltaT of the air the more heat will be = removed even with the slower velocity and mass flow ( the drag would = also be reduced, just had to throw that one in {:>)).=20 Ok, I'll let you slow down the air for the thicker RAD. But then I am = going to slow the air for the thin RAD even more than that. Afterward, we can both make a fortune selling my new idea: = Seven-minute Ab videos! =20 (and maybe radiators that need no air at all) :-) Tracy Crook Wrote: This is where it starts to go badly wrong and/or misses the whole=20 point. The main object of using a thick rad is to use fewer CFM=20 (lower mass flow rate). If you want to assume same mass flow, = there is no advantage (and probably a disadvantage) for a thick rad. Ah HA! You heard it folks, right there in black and white. If 2.75" IS a thick rad, then I must be on your side of the discussion = all along, as my rad is 3" thick. Yet it is as wide and long as I could = reasonably fit under the cowl. =20 This brings me to my final point (promise I won't make anymore = points). Use the widest-thinnest radiator you can reasonably fit under = the cowl and make appropriate ducting. I guarantee that you don't want = to use the thickest-narrowest rad you can fit. That would not cool well = at all.=20 --=20 David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net ------=_NextPart_000_0004_01C827D6.F90B2180 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ok, Dave, Just to enable you to keep = your=20 promise of not making any more points, I will refrain from my crushing = rebuttal=20 along the lines of your thin rad running out of mass flow before I run = out of=20 DeltaT {:>)
 
I 'm afraid I agree with Monty's assessment of = it being a=20 sort of snipe hunt at our level of resources and that since we are most = often=20 fitting our cooling systems into airframes not designed for liquid = cooling=20 everything ends up being a compromise which fortuitously works (most of = the=20 time).
 
I think it was a good topic and got wrung out = fairly well=20 - whichever side of the core you are on {::>)
 
Ed
 
 
----- Original Message -----
From:=20 David=20 Leonard
Sent: Thursday, November 15, = 2007 10:14=20 PM
Subject: [FlyRotary] Re: Thick = vs Thin=20 was : Diffuser Configuration Comparison

Ed Anderson Wrote:
So IF in installing the thicker core, I slow down the = mass flow=20 through the duct by 1/2  (which I can easily do - increasing it = might=20 be more difficult) then the air velocity through the core will be=20 reduced.  With the velocity decreased, the air will take longer = to=20 transverse the core.  The longer the air takes to move through = the core=20 the more heat it will absorb, the more heat the air absorbs the = greater the=20 DeltaT of the air.  The greater the deltaT of the air the more = heat=20 will be removed even with the slower velocity and mass flow ( the = drag would=20 also be reduced, just had to throw that one in {:>)).=20

Ok, I'll let you slow down the air for the = thicker=20 RAD.  But then I am going to slow the air for the thin RAD even = more than=20 that.

Afterward, we can both make a fortune selling my new = idea:=20 Seven-minute Ab videos! 
(and maybe radiators that need no = air at=20 all)   :-)

Tracy Crook Wrote:
This=20 is where it starts to go badly wrong and/or misses the whole =
point.=20  The main object of using a thick rad is to use fewer CFM =
(lower=20 mass flow rate).   If you want to assume same mass flow, = there
is no=20 advantage (and probably a disadvantage) for a thick rad.
 
Ah HA!  You heard it folks, right there in = black=20 and white.

If 2.75" IS a thick rad, then I must be on your side = of the=20 discussion all along, as my rad is 3" thick.  Yet it is as wide = and long=20 as I could reasonably fit under the cowl. 

This brings me = to my=20 final point (promise I won't make anymore points).  Use the=20 widest-thinnest radiator you can reasonably fit under the cowl and = make=20 appropriate ducting.  I guarantee that you don't want to use the=20 thickest-narrowest rad you can fit.  That would not cool well at = all.=20

--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net=20 ------=_NextPart_000_0004_01C827D6.F90B2180--