X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0c5) with ESMTP id 776373 for flyrotary@lancaironline.net; Fri, 21 Oct 2005 22:40:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j9M2dUWf029087 for ; Fri, 21 Oct 2005 22:39:31 -0400 (EDT) Message-ID: <001001c5d6b1$d5cdffd0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: specific heat of air Date: Fri, 21 Oct 2005 22:39:33 -0400 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine Specific Heat (Cp) Density Specific Gravity Specific Heat (Cp) Temp. Pressure Temp. Pressure Density Substance Chemical Symbol Mol. Weight ° F BTU/lb Air = 1 BTU/lb °F lb/cu. ft Water = 1 BTU/lb °F °F psia °F psia lb/cu ft Air -- 28.98 -317.8 88.2 1 0.241 0.08018 You are correct Bob, I always use the cp for BTU/LBm/F which as you and the chart point out is 0.241 BTU/Lbm/F(for 32F), and just assumed that's the units that Al was using. Should have read it more carefully Al's use of BTU/CubicFoot/F I use BTU/LBM/F as that gives me the opportunity to throw in the air density (via the Lbm) to determine the heat transferred at various altitudes. Ed ----- Original Message ----- From: "Bob White" To: "Rotary motors in aircraft" Sent: Friday, October 21, 2005 9:25 PM Subject: [FlyRotary] Re: specific heat of air > Hi Ed, > > Al's number was .02 BTU/cu-ft. - F and your number is 0.241 BTU/lb - F. > Per the web site you mentioned, density is given as 0.08018 lb/cu-ft. > So if I'm doing the conversion in the right direction: > 0.241 X 0.08= 0.019 which is about 0.02. > > Are both numbers correct? > > Bob W. > > > > On Fri, 21 Oct 2005 20:46:02 -0400 > "Ed Anderson" wrote: > >> Al, I went back to some of my spreadsheets and I have for constant >> pressure (Cp) as >> >> 0.25 BTU/Lbm/F >> >> Here is web site which gives it as 0.241 BTU/LBM/F at 32F Sea Level >> >> http://www.uigi.com/physical_prop_e.html >> >> So looks like you have the decimal off a bit. >> >> Sorry, it took me so long, been out at the aircraft all day putting on >> the new right gear leg, and brakes, etc. >> >> Ed A >> >> >> >> >> ----- Original Message ----- >> From: Al Gietzen >> To: Rotary motors in aircraft >> Sent: Friday, October 21, 2005 2:59 PM >> Subject: [FlyRotary] specific heat of air >> >> >> Ed, or Bill, or somebody; help me out here. I was reviewing my calcs >> for air flow requirements, and find I used 0.02 Btu/cu. ft -F for the >> specific heat of air. I don't know where that came from, and can only >> find it in joules/Kg - K. By the time I do all the conversions to >> British units and mass to volume I now get quite a different number. >> >> >> >> What is a good number for air at about 1 atmosphere and, say 90F; in >> Btu per cu ft per degree F? >> >> >> >> Thanks, >> >> >> >> Al >> > > > -- > http://www.bob-white.com > N93BD - Rotary Powered BD-4 (projected engine start in November) > Custom Cables for your rotary installation - > http://www.roblinphoto.com/shop/ > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/