Return-Path: Sender: (Marvin Kaye) To: flyrotary@lancaironline.net Date: Fri, 05 Dec 2003 20:40:59 -0500 Message-ID: X-Original-Return-Path: Received: from fed1mtao07.cox.net ([68.6.19.124] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2790393 for flyrotary@lancaironline.net; Fri, 05 Dec 2003 20:12:15 -0500 Received: from smtp.west.cox.net ([172.18.180.57]) by fed1mtao07.cox.net (InterMail vM.5.01.06.05 201-253-122-130-105-20030824) with SMTP id <20031206011133.QCJH14590.fed1mtao07.cox.net@smtp.west.cox.net> for ; Fri, 5 Dec 2003 20:11:33 -0500 From: Dale Rogers X-Original-To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] K&M and Thick Radiators X-Original-Date: Fri, 5 Dec 2003 20:11:36 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Original-Message-Id: <20031206011133.QCJH14590.fed1mtao07.cox.net@smtp.west.cox.net> Ed, It looks like you and I were coming to similar conclusions. My present plan for my, as yet, unstarted Cozy (unless one counts completion of the shop facilities) is to mount two cores - e.g. the Frigidaire EV6709 - in tandem, with the water flow going first through the rear core and then through the front one. The delta-T won't be *ideal* in either core, but it will be substantial. I just have to work out a plenum that allows no air leakage between the cores. Still trying to keep the expenses down, without being "cheap". Dale R. > In essence, they make the statement that thicker radiators with closer fin > spacing provides for more heat dissapation into an airstream. The > refer to the thickness as "L" length of the cooling block (heat exchanger) > and the "D" the hydraulic wetted area spacing (basically related to the fin > area/spacing) . Re is the Reyonlds number which is smaller with lower > velocity. > > So a low velocity airflow through a thick radiator (L) with close fin > spacing (D) is the way I interpret their words and equation for the heat > transfer coefficient "k". This would mean you need good pressure recovery > from a diffuser (low velocity out of your diffuser). So long as you have > the dynamic pressure (read that as having adequate airspeed through your > inlet) for the thickness you are using, it appears that you are ahead of the > game using a thicker radiator. > > This makes sense (to me) in that a thicker > radiator continues to dump heat into the airstream as long as the air is > passing through it - even thought it becomes less efficient at this transfer > as the air through it heats up (thereby reducing the "Delta T"), it is still > transfering heat to the air.