Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Mon, 24 Mar 2003 19:24:27 -0500 Message-ID: X-Original-Return-Path: Received: from [65.54.169.57] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.1b1) with ESMTP id 2085204 for flyrotary@lancaironline.net; Mon, 24 Mar 2003 18:58:54 -0500 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Mon, 24 Mar 2003 15:58:53 -0800 Received: from 65.137.50.11 by bay3-dav27.bay3.hotmail.com with DAV; Mon, 24 Mar 2003 23:58:51 +0000 X-Originating-IP: [65.137.50.11] X-Originating-Email: [lors01@msn.com] Reply-To: "Tracy Crook" From: "Tracy Crook" X-Original-To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Thick or Thin? X-Original-Date: Mon, 24 Mar 2003 18:58:24 -0500 Organization: Real World Solutions Inc. MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Original-Message-ID: X-OriginalArrivalTime: 24 Mar 2003 23:58:53.0628 (UTC) FILETIME=[52E4EFC0:01C2F261] ----- Original Message ----- From: To: "Rotary motors in aircraft" Sent: Monday, March 24, 2003 6:18 PM Subject: [FlyRotary] Re: Thick or Thin? > Hi All, > > Would someone please help me better understand the physics involved with this? > > It appears to me that, especially given the airspeeds we're talking about, as long as there is significant temperature differential between the air and the tube/fin at the trailing end of the air path, the radiator is working. > Isn't it the case that our biggest concerns with thick cores are (1) saturation of the airstream, (2) weight per transferred BTU, (3) drag? > > So, for a given transfer rate, one might expect a thick core radiatior to be heavier than a thin one, but offer less drag. If the load due to additional weight is less than the drag of the lighter thin core, aren't we ahead? > > Dale Your observations are correct Dale, but in reality the weigh factor is insignificant. Of course there is a limiting factor on how far we can go with thick rads. At some point there is not enough dynamic pressure to push enough air through a very thick rad to carry away the required BTUs, even if the air is heated to the theoretical limit equal to (almost) the coolant temperature. An airplane flying at 200 MPH has a lot of dynamic pressure potential so the limit is relatively high (compared to passenger cars). It is worth noting that the dynamic pressure at only 120 mph is enough to support the weight of your body. 120 MPH is the terminal velocity of a sky diver in free fall. Tracy Crook