Return-Path: Received: from gull.mail.pas.earthlink.net ([207.217.120.84] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2883599 for flyrotary@lancaironline.net; Tue, 09 Dec 2003 13:12:50 -0500 Received: from h-68-166-182-146.sfldmidn.covad.net ([68.166.182.146] helo=richard) by gull.mail.pas.earthlink.net with smtp (Exim 3.33 #1) id 1ATmLo-00005n-00 for flyrotary@lancaironline.net; Tue, 09 Dec 2003 10:12:48 -0800 Message-ID: <002701c3be80$2ddd1220$6601a8c0@richard> From: "Eric Ruttan" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air Density at altitude Date: Tue, 9 Dec 2003 13:13:42 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0024_01C3BE56.449C1350" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_0024_01C3BE56.449C1350 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable If you look at the DeltaT (DT) for cooling; aircooled have a much larger = DT than liquid. At altitude the increase in DT for aircooled aircraft = is small, but in liquid aircraft it is large. So you can say this several ways. Liquid Cooled aircraft have more of an advantage at altitude. Or (perhaps more correctly) Air cooled aircraft have less of a large advantage at altitude. ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Tuesday, December 09, 2003 12:32 PM Subject: [FlyRotary] Re: Air Density at altitude 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_0024_01C3BE56.449C1350 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
If you look at the DeltaT (DT) for = cooling;=20 aircooled have a much larger DT than liquid.  At altitude the = increase in=20 DT for aircooled aircraft is small, but in liquid aircraft it is=20 large.
 
So you can say this several = ways.
 
Liquid Cooled aircraft have more of an = advantage at=20 altitude.
Or (perhaps more = correctly)
Air cooled aircraft have less of a = large advantage=20 at altitude.
 
----- Original Message -----
From:=20 Ed=20 Anderson
Sent: Tuesday, December 09, = 2003 12:32=20 PM
Subject: [FlyRotary] Re: Air = Density at=20 altitude

 
 
From:=20 JJ=20 JOHNSON
To: Rotary motors in = aircraft=20
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=20 cooled a/c cool better at altitude than their aircooled = counterparts. Anyone=20 else heard this?
 
Jarrett Johnson
 
Interesting point.  It = certainly has to=20 help 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). =20 The question is would is how much would it help and would it help = enough to=20 make up for the lesser air mass flow? The mass flow at 20,000 ft is = approx=20 30% less than that at sea level for the same indicated air=20 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=20 Cp doesn't change that much)  it would appear that means the = delta T=20 term would need to increase by 30% for Q quantity to remain the = same. =20 But, I don't know exactly how a 79Deg colder incoming air would = affect the=20 Delta T term.
 
BIll??
 
Ed Anderson
 
 
------=_NextPart_000_0024_01C3BE56.449C1350--