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 5.0.4) with ESMTP id 893750 for flyrotary@lancaironline.net; Fri, 23 Dec 2005 11:21:09 -0500 Received-SPF: pass receiver=logan.com; client-ip=166.102.165.170; envelope-from=montyr2157@alltel.net Received: from Thorstwin ([4.226.237.173]) by ispmxmta09-srv.alltel.net with SMTP id <20051223162024.NRWC12342.ispmxmta09-srv.alltel.net@Thorstwin> for ; Fri, 23 Dec 2005 10:20:24 -0600 Message-ID: <000901c607dc$ca80dc40$adede204@Thorstwin> From: "Monty Roberts" To: Subject: cooling/TAS vs IAS Date: Fri, 23 Dec 2005 10:20:28 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01C607AA.7F339700" 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_0006_01C607AA.7F339700 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Let me see if I've got this right. "q" is dynamic pressure, correct? = As best I recall the equation for dynamic pressure is 1/2pV^2 with p = being air density and V velocity.=20 So if I understand you correctly, it appears that even for IAS - the = case is we are using TAS (actual velocity of air molecules - or = aircraft) to generate the dynamic pressure in the pitot tube that gives = us an indication - we know as IAS? So I guess its correct to say IAS is = a reflection of "q" but the indication is actually a result of air = density and TAS, Correct?? I certainly understand your argument for TAS as being the speed of = the molecules and therefore the rate at which they carry away heat. = Its just I would have bet money that if you wanted to test the effects = of different ambient tempts on a core, you would ensured that they both = saw the same dynamic pressure. In order to do that, of course, at = higher altitude you would need a greater true airspeed (due to the lower = density) in order to get the same IAS (dynamic pressure) as you would = have at a lower altitude (denser air with less TAS). But, you live and learn. Getting older and none the swifter {:>) Ed A Sounds like you got it. There is no apples to apples in this case. The = only apples to apples is same pressure, lower T1 same heat rejection. Of = course density will be higher and Dt will be lower. The only apples I'm interested in is the same fuel flow (heat rejection) = Everything else will be different and I want to know how much so I can = make a guestimate of heat exchanger effectiveness.=20 What method did you use in your math models for the heat exchangers? = LMTD or NTU? Monty ------=_NextPart_000_0006_01C607AA.7F339700 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Let me see if I've got = this=20 right. "q" is dynamic pressure, correct? As best I recall = the=20 equation for dynamic pressure is 1/2pV^2 with p being air density = and V=20 velocity.

So if I = understand you=20 correctly, it appears that even for IAS - the case is = we are=20 using TAS (actual velocity of air molecules - or aircraft) to = generate=20 the dynamic pressure in the pitot tube that gives us an = indication -=20 we know as IAS? So I guess its correct to say IAS is a reflection = of "q"=20 but the indication is actually a result of air density and TAS,=20 Correct??

I = certainly=20 understand your argument for TAS as being the speed of the molecules and = therefore the rate at which they carry away heat. Its = just I=20 would have bet money that if you wanted to test the effects of different = ambient=20 tempts on a core, you would ensured that they both saw the same dynamic=20 pressure. In order to do that, of course, at higher altitude = you=20 would need a greater true airspeed (due to the lower = density) in=20 order to get the same IAS (dynamic pressure) as you would have at a = lower=20 altitude (denser air with less TAS).

But, you live and = learn.

Getting older and none = the swifter=20 {:>)

Ed A

Sounds like you got it. There is no = apples to=20 apples in this case. The only apples to apples is same pressure, lower = T1 same=20 heat rejection. Of course density will be higher and Dt will be=20 lower.

The only apples I'm interested in is = the same fuel=20 flow (heat rejection) Everything else will be different and I want to = know how=20 much so I can make a guestimate of heat exchanger effectiveness. =

What method did you use in your math = models for the=20 heat exchangers? LMTD or NTU?

Monty

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