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 5.2c2) with ESMTP id 2471991 for flyrotary@lancaironline.net; Wed, 14 Nov 2007 11:20:51 -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 <20071114162011.WUIA507.cdptpa-omta06.mail.rr.com@edward2> for ; Wed, 14 Nov 2007 16:20:11 +0000 Message-ID: <001301c826da$8a29a450$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Rebutal to the rebutal {:>) Thick vs Thin was : Diffuser Configuration Comparison Date: Wed, 14 Nov 2007 11:22:23 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0010_01C826B0.A115A8F0" 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_0010_01C826B0.A115A8F0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable =20 > Ed Anderson wrote: >> Q =3D m cp DeltaT. Clearly shows that heat removal is proportional = to BOTH mass flow AND deltaT (as well as the specific heat but that is = fixed by nature). Yet, for some reason that I still don't understand, = you skeptics seem to fixate on the mass flow factor {:>) and ignore = DeltaT as if it were a factor you can do nothing about. =20 >> =20 > I think that is because you're reducing mass flow for the thick rad. =20 > You could do the same for the thin rad, and end with the same deltaT. = > To fairly compare the radiators, you have to fix the airflow at the=20 > inlet and decide which option you can get to dump the most heat into = the=20 > air while offering the least drag. Ok, good point!, I agree. I think part of the problem is the way I = framed the question when I started out. I should have made it clearer = than what I was really looking for was which radiator gave me the best = cooling system. Then that probably requires coming up with a critera = about what consitutes "best", do we also need to factor in weight, size, = cost, etc?? Don't know, but ultimately we are interested first in = cooling the engine - if the cooling system does not do that then it = doesn't matter thin, thick, fast, slow, low/high drag, etc. I understand your point about fixing the air mass flow and then making = the comparison based on that, but, my counter is - why not base it on = the amount of heat removed by the system rather than air flow. We know = that mass flow by itself is only part of the equation and the real = objective is to remove heat. Clearly, with everybody taking exception to my analysis/reasoning it = raises the old question along the lines ".... either I'm the only sane = one or....." {:>). Guess I am going to have to sit down and based on this discussion try = some real numbers and sizes to make some comparisons (along with the = assumptions, assertations, etc) for a complete cooling system and see = where that leads me Thanks for the input, Ernest. Gotta remember to compare the same fruite = {:>) =20 Ed . =20 =20 > Of course, out here in the real world it doesn't work that way. =20 > Everything affects everything else, and we have to design the whole=20 > system. We rely on generalities and ROTs, and hope that we wind up = with=20 > something that has a passing aquaintence with "optimized". Most of us = > will settle for a not to distant relative of "it works". >=20 > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0010_01C826B0.A115A8F0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
 
> Ed Anderson wrote:
>>  Q =3D = m cp=20 DeltaT.  Clearly shows that heat removal is proportional to BOTH = mass flow=20 AND deltaT (as well as the specific heat but that is fixed by=20 nature).   Yet, for some reason that I still don't understand, = you=20 skeptics seem to fixate on the mass flow factor {:>) and ignore = DeltaT as if=20 it were a factor you can do nothing about.  =
>>  =20
> I think that is because you're reducing mass flow for the thick = rad. 
> You could do the same for the thin rad, and end with = the=20 same deltaT. 
> To fairly compare the radiators, you have to = fix the=20 airflow at the
> inlet and decide which option you can get to = dump the=20 most heat into the
> air while offering the least = drag.
Ok, good point!,  I=20 agree.    I think part of the problem is the way I = framed=20 the question when I started out.  I should have made it clearer = than what I=20 was really looking for was which radiator gave me the best cooling = system. =20 Then that probably requires coming up with a critera about what = consitutes=20 "best", do we also need to factor in weight, size, cost, etc??  = Don't know,=20 but ultimately we are interested first in cooling the engine - if the = cooling=20 system does not do that then it doesn't matter thin, thick, fast, slow, = low/high=20 drag, etc.
 
I understand your point about = fixing the air=20 mass flow and then making the comparison based on that, but, my counter = is - why=20 not base it on the amount of heat removed by the system rather than air=20 flow.  We know that mass flow by itself is only part of the = equation and=20 the real objective is to remove heat.
 
  Clearly, with everybody = taking=20 exception to my analysis/reasoning it raises the old question along the = lines=20 ".... either I'm the only sane one or....." {:>).
 
Guess I am going to have to sit = down and=20 based on this discussion try some real numbers and sizes to make some=20 comparisons (along with the assumptions, assertations, etc) for a = complete=20 cooling system and see where that leads me
 
Thanks for the input, Ernest. = Gotta remember=20 to compare the same fruite {:>) 
 
Ed
 
. 
 
 
> Of course, out here in the real = world it=20 doesn't work that way. 
> Everything affects everything = else, and we=20 have to design the whole
> system.  We rely on generalities = and=20 ROTs, and hope that we wind up with
> something that has a = passing=20 aquaintence with "optimized".  Most of us
> will settle for = a not to=20 distant relative of "it works".
>
> --
> = Homepage: =20 http://www.flyrotary.com/
> Archive=20 and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html
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