Return-Path: Received: from fed1rmmtao06.cox.net ([68.230.241.33] verified) by logan.com (CommuniGate Pro SMTP 4.2.3) with ESMTP id 433005 for flyrotary@lancaironline.net; Sun, 26 Sep 2004 12:54:45 -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 <20040926165412.INWG5569.fed1rmmtao06.cox.net@BigAl> for ; Sun, 26 Sep 2004 12:54:12 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Oil viscosity Date: Sun, 26 Sep 2004 09:54:26 -0700 Message-ID: <000001c4a3e9$7b395980$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C4A3AE.CEDCCB70" 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_01C4A3AE.CEDCCB70 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable 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 Definitely not BS, so your cosmic egg can remain intact. In the pan the = oil is essentially static, so there is a major boundary layer conduction = issue. In any well designed oil cooler with narrow high-velocity channels with internal fins or turbulators - - Ah-h-h; hold it right there, the AC = core doesn't qualify. Or are you using a well designed oil cooler? =20 But that is what I meant by a slightly better heat transfer coefficient = with lower viscosity; less boundary layer effect. =20 In a couple weeks, we'll see if there's any real difference in temps. =20 =20 That will tell the tale. Good luck with your fittings, =20 Al =20 ------=_NextPart_000_0001_01C4A3AE.CEDCCB70 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

  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 = :-) 

 

Definitely = not BS, so your cosmic egg can remain intact.  In the pan the oil is = essentially static, so there is a major boundary layer conduction issue.  In = any well designed oil cooler with narrow high-velocity channels with internal = fins or turbulators - - Ah-h-h; hold it right there, the AC core doesn’t = qualify.  Or are you using a well designed oil cooler?

 <= /font>

But that is = what I meant by a slightly better heat transfer coefficient with lower = viscosity; less boundary layer effect.

 

In a couple = weeks, we'll see if there's any real difference in temps. 

 

That will = tell the tale.

Good luck = with your fittings,

 <= /font>

Al

 

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