Return-Path: <eanderson@carolina.rr.com>
Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com)
  by logan.com (CommuniGate Pro SMTP 4.1.8)
  with ESMTP id 2881619 for flyrotary@lancaironline.net; Mon, 08 Dec 2003 09:10:55 -0500
Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20])
	by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id hB8EAod3029926
	for <flyrotary@lancaironline.net>; Mon, 8 Dec 2003 09:10:53 -0500 (EST)
Message-ID: <000e01c3bd94$a2ef3120$1702a8c0@WorkGroup>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2881247@logan.com>
Subject: Re: [FlyRotary] Re: K&M and Thick Radiators
Date: Mon, 8 Dec 2003 09:07:37 -0500
MIME-Version: 1.0
Content-Type: multipart/alternative;
	boundary="----=_NextPart_000_000B_01C3BD6A.B9BD9BA0"
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_000B_01C3BD6A.B9BD9BA0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable


=20

> <... How do the Mass Air requirements change with altitude ...>
> They don't, except as the heat rejection requirements change.
> You get the same mass airflow at 180 kias at sea level or 15 k ft. Of =
course
> your TRUE airspeed at 15k is a lot higher and that's what pumps more =
of the
> thinner air through the system.  Also, to the extent that fuel flow is =
less at
> 15 k ft, so you have less heat rejection requirements and therefore =
less mass
> flow requirements.
>=20
> <... if the fuel burn was 8.5gph and altitude was 25K ...>
> .... you'd be making about 300 kts TAS and would no doubt have the =
same mass
> airflow as at SL 8.5 gph.
>=20
> Mass airflow is a function of indicated airspeed which is dynamic =
pressure which
> is how many molecules are going past a point in a unit of time.
>=20
> Just a theory ... Jim S.
>=20

One common formula for air mass flow is as follows:


W =3D p*V*A

Where W is air mass flow either in Slugs/Unit time or pounds mass (lbm) =
or kilograms/unit time, etc.  p is the density of the air mass, V the =
velocity of the air stream and A the area of the duct (or what ever) you =
have the air flowing through.

A formula for Dynamic pressure on the other hand is=20

Pd =3D 1/2pV^2

 which results in units of pressure (lbf - pound force per square foot, =
square inch, square CM or other such area units.  So Dynamic pressure =
and air mass flow are two separate things.  However, density and =
velocity of the air are a factor in both.=20

You can have high dynamic pressure and low mass flow or vise versa. =
Velocity (V^2) is the dominate factor in dynamic pressure whereas volume =
(V*A) is the dominate factor in dynamic pressure. =20

FWIW

Ed Anderson
------=_NextPart_000_000B_01C3BD6A.B9BD9BA0
Content-Type: text/html;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2800.1264" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>&nbsp;<BR></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>&gt; &lt;... How do the Mass Air =
requirements=20
change with altitude ...&gt;<BR>&gt; They don't, except as the heat =
rejection=20
requirements change.<BR>&gt; You get the same mass airflow at 180 kias =
at sea=20
level or 15 k ft. Of course<BR>&gt; your TRUE airspeed at 15k is a lot =
higher=20
and that's what pumps more of the<BR>&gt; thinner air through the =
system.&nbsp;=20
Also, to the extent that fuel flow is less at<BR>&gt; 15 k ft, so you =
have less=20
heat rejection requirements and therefore less mass<BR>&gt; flow=20
requirements.<BR>&gt; <BR>&gt; &lt;... if the fuel burn was 8.5gph and =
altitude=20
was 25K ...&gt;<BR>&gt; .... you'd be making about 300 kts TAS and would =
no=20
doubt have the same mass<BR>&gt; airflow as at SL 8.5 gph.<BR>&gt; =
<BR>&gt; Mass=20
airflow is a function of indicated airspeed which is dynamic pressure=20
which<BR>&gt; is how many molecules are going past a point in a unit of=20
time.<BR>&gt; <BR>&gt; Just a theory ... Jim S.<BR>&gt; =
<BR></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>One common formula for air mass flow is =
as=20
follows:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D4><STRONG>W =3D =
<EM>p</EM>*V*A</STRONG></FONT></DIV>
<DIV><STRONG><FONT face=3DArial size=3D4></FONT></STRONG>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Where W is air mass flow either in =
Slugs/Unit time=20
or pounds mass (lbm) or kilograms/unit time, etc.&nbsp; p is the density =
of the=20
air mass, V the velocity of the air stream and A the area of the duct =
(or what=20
ever) you have the air flowing through.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>A formula for Dynamic pressure on the =
other hand is=20
</FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D4><STRONG>Pd =3D =
1/2pV^2</STRONG></FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial><FONT size=3D2><FONT>&nbsp;which results in =
units of=20
pressure (lbf - pound force per square foot, square inch, square CM or =
other=20
such area units.&nbsp; So Dynamic pressure and air mass flow are two =
separate=20
things.&nbsp; However, density and velocity of the air are a factor in=20
both.</FONT> </FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>You can have high dynamic pressure and =
low mass=20
flow or vise versa. Velocity (V^2)&nbsp;is the dominate factor in =
dynamic=20
pressure whereas volume (V*A) is the dominate factor in dynamic =
pressure.&nbsp;=20
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>FWIW</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Ed Anderson</FONT></DIV></BODY></HTML>

------=_NextPart_000_000B_01C3BD6A.B9BD9BA0--