Return-Path: Received: from [65.54.169.65] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2642806 for flyrotary@lancaironline.net; Sun, 19 Oct 2003 17:13:09 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sun, 19 Oct 2003 14:13:08 -0700 Received: from 65.137.50.122 by bay3-dav35.bay3.hotmail.com with DAV; Sun, 19 Oct 2003 21:13:08 +0000 X-Originating-IP: [65.137.50.122] X-Originating-Email: [lors01@msn.com] Reply-To: "Tracy Crook" From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Water pumps Somebody STOP me! Date: Sun, 19 Oct 2003 17:15:45 -0400 Organization: Real World Solutions Inc. MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00FC_01C39664.A202E2E0" 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: 19 Oct 2003 21:13:08.0729 (UTC) FILETIME=[CB9B8690:01C39685] This is a multi-part message in MIME format. ------=_NextPart_000_00FC_01C39664.A202E2E0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Tracy wrote 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). ----------------------------- Tracy, I agree with you with respect to the amount of energy being = used to pump water, however the frictional losses in the pump increase = with rpm and decreasing flow. The point I was trying to make = (apparently poorly) is that the power dissipated in the pump can rise = rapidly with RPM. The energy into the pump is turned into heat energy, = and although this effect is small at lower RPM, it rises rather quickly = with RPM. A water brake dynomometer is just a pump that is dumping its energy = into raising the temperature of the water. Bill Schertz All true. But my point was that there is still *less* shaft HP = required to turn the pump when the thermostat restricts the flow through = the pump and we are not wasting engine HP by having a restriction in the = circuit as is occasionally claimed. True, the pump is operating in a = less efficient part of its operating curve, but do we really care? Tracy ------=_NextPart_000_00FC_01C39664.A202E2E0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Tracy wrote
 
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).
 
-----------------------------
Tracy, I agree with you with respect = to the=20 amount of energy being used to pump water, however the frictional = losses in=20 the pump increase with rpm and decreasing flow.  The point I was = trying=20 to make (apparently poorly) is that the power dissipated in the pump = can rise=20 rapidly with RPM. The energy into the pump is turned into heat energy, = and=20 although this effect is small at lower RPM, it rises rather quickly = with=20 RPM.
 
A water brake dynomometer is just a = pump that is=20 dumping its energy into raising the temperature of the = water.
 
Bill Schertz
 
All true.  But my point was that = there is=20 still *less* shaft HP required to turn the pump when the thermostat = restricts=20 the flow through the pump and we are not wasting engine HP by having a = restriction in the circuit as is occasionally claimed.  True, the = pump is=20 operating in a less efficient part of its operating curve, but do we = really=20 care?
 
Tracy
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