Return-Path: <13brv3@bellsouth.net> Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.2.3) with ESMTP id 432934 for flyrotary@lancaironline.net; Sun, 26 Sep 2004 11:01:00 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.69; envelope-from=13brv3@bellsouth.net Received: from rd ([65.6.194.9]) by imf21aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20040926150031.PIJI1791.imf21aec.mail.bellsouth.net@rd> for ; Sun, 26 Sep 2004 11:00:31 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Oil viscosity Date: Sun, 26 Sep 2004 10:00:50 -0500 Message-ID: <01f001c4a3d9$9c7cc5b0$04000100@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01F1_01C4A3AF.B3A6BDB0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 In-Reply-To: Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_01F1_01C4A3AF.B3A6BDB0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Well, no; but. The specific heat is the same and the flow rate around = the loop is (roughly) the same. The lower viscosity will result in more = flow through the bearings and rotors (less bypassing through the pressure = control valve) providing more effective cooling of the rotors. Well that's actually a bonus that I wasn't considering.=20 But it has little effect on the heat rejection (other than slightly = better heat transfer coefficient), so, one might expect the oil to heat up at = the same rate, or a bit faster. I've always read that it was difficult to cool oil because it tends to = cling to the surface. Specifically, when the subject of cooling oil in the = pan comes up, someone always points out that oil clings to the cooler pan surface, and gets a little thicker, allowing other hot oil to just flow = over the top of that film of thicker oil. In other words, the oil flows past without making any real contact with the relatively cool pan surface. I always figured this same thing happened to some extent in the tubes of = oil coolers as well. So go ahead, shatter my mental reality and tell me = this is all BS :-) =20 =20 Unless there is something major I'm missing. =20 In a couple weeks, we'll see if there's any real difference in temps. = If not, you aren't missing anything major :-) =20 Thanks, Rusty (@$*^& Earl's fittings) =20 ------=_NextPart_000_01F1_01C4A3AF.B3A6BDB0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

Well, no; but. The specific heat is the same and the = flow rate=20 around the loop is (roughly) the same.  The lower viscosity will = result in=20 more flow through the bearings and rotors (less bypassing through the = pressure=20 control valve) providing more effective cooling of the = rotors.

Well that's actually a bonus that = I wasn't=20 considering.

  But it has little effect on the heat rejection = (other=20 than slightly better heat transfer coefficient), so, one might expect = the oil to=20 heat up at the same rate, or a bit faster.

I've = always read that it=20 was difficult to cool oil because it tends to cling to the = surface. =20 Specifically, when the subject of cooling oil in the pan comes up, = someone=20 always points out that oil clings to the cooler pan surface, and gets a = little=20 thicker, allowing other hot oil to just flow over the top of that film = of=20 thicker oil.  In other words, the oil flows past without making any = real=20 contact with the relatively cool pan surface.  I always = figured this=20 same thing happened to some extent in the tubes of oil coolers as = well.  So=20 go ahead, shatter my mental reality and tell me this is all BS :-)  =
 
Unless there is something major I’m = missing.
 
In a = couple weeks, we'll=20 see if there's any real difference in temps.  If not, you aren't = missing=20 anything major :-)
 
Thanks,
Rusty = (@$*^& Earl's=20 fittings)
 


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