Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2883565 for flyrotary@lancaironline.net; Tue, 09 Dec 2003 12:36:28 -0500 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id hB9HaKxk028228 for ; Tue, 9 Dec 2003 12:36:22 -0500 (EST) Message-ID: <003e01c3be7a$772e0ca0$1702a8c0@WorkGroup> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air Density at altitude Date: Tue, 9 Dec 2003 12:32:47 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003B_01C3BE50.8D4B76A0" 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-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_003B_01C3BE50.8D4B76A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =20 From: JJ JOHNSON=20 To: Rotary motors in aircraft=20 Sent: Tuesday, December 09, 2003 11:54 AM Subject: [FlyRotary] Re: Air Density at altitude Ed another factor which will help in this situation is the fact that = the air at 25K will be alot colder than at S.L. That will help as well = won't it? I've read somewhere that liquid cooled a/c cool better at = altitude than their aircooled counterparts. Anyone else heard this? Jarrett Johnson Interesting point. It certainly has to help as the colder incoming = air will provide a larger Delta T between the temperature of the = incoming air and the walls/fins of the cooler core (which would stay at = approx the same temp - if using a thermostat). The question is would is = how much would it help and would it help enough to make up for the = lesser air mass flow? The mass flow at 20,000 ft is approx 30% less than = that at sea level for the same indicated air speed. Heat transfer equation Q =3DW*DeltaT*Cp, with W =3D mass flow down by = 30%. So to get rid of the same Q of heat (and since Cp doesn't change = that much) it would appear that means the delta T term would need to = increase by 30% for Q quantity to remain the same. But, I don't know = exactly how a 79Deg colder incoming air would affect the Delta T term. BIll?? Ed Anderson ------=_NextPart_000_003B_01C3BE50.8D4B76A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
 
From:=20 JJ=20 JOHNSON
Sent: Tuesday, December 09, = 2003 11:54=20 AM
Subject: [FlyRotary] Re: Air = Density at=20 altitude

Ed another factor which will help in = this=20 situation is the fact that the air at 25K will be alot colder than at = S.L.=20 That will help as well won't it?  I've read somewhere that liquid = cooled=20 a/c cool better at altitude than their aircooled counterparts. Anyone = else=20 heard this?
 
Jarrett Johnson
 
Interesting point.  It certainly = has to help=20 as the colder incoming air will provide a larger Delta T between the=20 temperature of the incoming air and the  walls/fins of the cooler = core=20 (which would stay at approx the same temp - if using a = thermostat).  The=20 question is would is how much would it help and would it help enough = to make=20 up for the lesser air mass flow? The mass flow at 20,000 ft is approx = 30% less=20 than that at sea level for the same indicated air speed.
 
Heat transfer equation Q = =3DW*DeltaT*Cp, with W =3D=20 mass flow down by 30%.  So to get rid of the same Q of heat (and = since Cp=20 doesn't change that much)  it would appear that means the delta T = term=20 would need to increase by 30% for Q quantity to remain the same.  = But, I=20 don't know exactly how a 79Deg colder incoming air would affect the = Delta T=20 term.
 
BIll??
 
Ed Anderson
 
 
------=_NextPart_000_003B_01C3BE50.8D4B76A0--