Return-Path: Received: from [65.54.168.121] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2629987 for flyrotary@lancaironline.net; Thu, 09 Oct 2003 10:02:00 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Thu, 9 Oct 2003 07:01:59 -0700 Received: from 65.137.51.197 by bay3-dav17.bay3.hotmail.com with DAV; Thu, 09 Oct 2003 14:01:59 +0000 X-Originating-IP: [65.137.51.197] X-Originating-Email: [lors01@msn.com] Reply-To: "Tracy Crook" From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: Water pumps Somebody STOP me! Date: Thu, 9 Oct 2003 10:04:29 -0400 Organization: Real World Solutions Inc. MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_005D_01C38E4C.BA5B2520" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Message-ID: X-OriginalArrivalTime: 09 Oct 2003 14:01:59.0328 (UTC) FILETIME=[E81CB200:01C38E6D] This is a multi-part message in MIME format. ------=_NextPart_000_005D_01C38E4C.BA5B2520 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Bill Schertz wrote: >huge snip< Dale and Jim make a good point about the water pump thrashing when the = thermostat closes -- drives up the power required. I bring this up occasionally to either: A. Dispell a popular myth or=20 B. Eliminate a big misunderstanding on my own part. I'll accept either outcome but so far no one has addressed the issue. = Based on everything I (think I ) know about pumps: Assumeing a constant pump speed, when the thermostat closes and head = pressure goes up, power required to drive the waterpump does NOT go up. = It actually goes DOWN. Reason: There is less mass being accelerated = (energy) at lower flow rates. In the extream example (zero flow) the = same water in the pump housing is being spun around at a constant = velocity which requires no energy. Of course there are losses in the = pump so the energy consumed is not zero. This argument applies ONLY to centrifugal pumps (of which automotive = waterpumps are an example) and not positive displacement types (like oil = pumps). OK, somebody shoot this argument down and educate me. Tracy ------=_NextPart_000_005D_01C38E4C.BA5B2520 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Bill Schertz wrote:

>huge snip<

Dale and Jim make a good point about = the water=20 pump thrashing when the thermostat closes -- drives up the power=20 required.

I bring this up occasionally to=20 either:

A. Dispell a popular = myth

or

B. Eliminate a big = misunderstanding on my=20 own part.

I'll accept either outcome but so far = no one has=20 addressed the issue. Based on everything I (think I ) know about = pumps:

Assumeing a constant pump speed, when = the=20 thermostat closes and head pressure goes up, power required to = drive the=20 waterpump does NOT go up. It actually goes DOWN. = Reason: =20 There is less mass being accelerated (energy) at lower flow = rates. In=20 the extream example (zero flow) the same water in the pump = housing is=20 being spun around at a constant velocity which requires no = energy. Of=20 course there are losses in the pump so the energy consumed is not=20 zero.

This argument applies ONLY to = centrifugal pumps=20 (of which automotive waterpumps are an example) and not positive=20 displacement types (like oil pumps).

OK, somebody shoot this argument down = and educate=20 me.

Tracy

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