Return-Path: Received: from fed1rmmtao06.cox.net ([68.230.241.33] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 480998 for flyrotary@lancaironline.net; Wed, 20 Oct 2004 20:28:17 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.33; envelope-from=ALVentures@cox.net Received: from BigAl ([68.107.116.221]) by fed1rmmtao06.cox.net (InterMail vM.6.01.03.04 201-2131-111-106-20040729) with ESMTP id <20041021002746.CUFD5664.fed1rmmtao06.cox.net@BigAl> for ; Wed, 20 Oct 2004 20:27:46 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: EWP Date: Wed, 20 Oct 2004 17:27:48 -0700 Message-ID: <000001c4b704$cb3d9760$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C4B6CA.1EDEBF60" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C4B6CA.1EDEBF60 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable =20 =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Dube Sent: Wednesday, October 20, 2004 12:00 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: EWP =20 Looking at the relationship between speed, flow and power dissipation, I come to a different conclusion. The pump output curve goes up = relatively linearly with speed and bends over toward flat as the back pressure = builds. The power dissipation required (with a prop) goes up roughly as the cube = of the speed (parabolically), so it goes up slowly at first and then heads = up pretty steep as you get past 3-4000 rpm.=20 Because the heat transfer behavior of the radiator and the = engine block are NOT simple functions of water flow, you really gain no insight = by doing simple flow calculations. You have to do the experiment, or do the computer model of the whole system. In reality, you would end up doing = both. The heat transfer formulas are very complicated and VERY = non-linear. Bill; You're right, of course. I was just looking at first principals; = ability of the coolant to carry heat from engine to radiator. That is linear and = is a function only of heat capacity, assumed delta T , and flow rate. That's = the first thing to consider for the design point you chose, and a condition = that has to be met. From there it is very complex on what the delta T = actually is. Yes, I suppose that inferring from this what the margin is at conditions off the design point is stretching it. Al =20 >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0001_01C4B6CA.1EDEBF60 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Dube
Sent: Wednesday, October 20, 2004 12:00 = PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = EWP

Looking at the relationship between speed, flow and = power dissipation, I come to a different conclusion. The pump output = curve goes up relatively linearly with speed and bends over toward flat as = the back pressure builds. The power dissipation required (with a prop) goes = up roughly as the cube of the speed (parabolically), so it goes up slowly = at first and then heads up pretty steep as you get past 3-4000 rpm. =

Because = the heat transfer behavior of the radiator and the engine block are NOT simple = functions of water flow, you really gain no insight by doing simple flow = calculations. You have to do the experiment, or do the computer model of the whole = system. In reality, you would end up doing both.

&nb= sp; The heat transfer formulas are very complicated and VERY non-linear. =

Bill;

You’re right, of course. I was just looking at first principals; ability = of the coolant to carry heat from engine to radiator. That is linear and = is a function only of heat capacity, assumed delta T , and flow rate. = That’s the first thing to consider for the design point you chose, and a = condition that has to be met. From there it is very complex on what the delta T = actually is. Yes, I suppose that inferring from this what the margin is at conditions off the design point is stretching it.

Al

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