Return-Path: Received: from fed1rmmtao03.cox.net ([68.230.241.36] verified) by logan.com (CommuniGate Pro SMTP 4.2b8) with ESMTP id 322361 for flyrotary@lancaironline.net; Thu, 15 Jul 2004 10:57:55 -0400 Received-SPF: error receiver=logan.com; client-ip=68.230.241.36; envelope-from=ALVentures@cox.net Received: from BigAl ([68.107.116.221]) by fed1rmmtao03.cox.net (InterMail vM.6.01.03.02 201-2131-111-104-20040324) with ESMTP id <20040715145724.JDEB10440.fed1rmmtao03.cox.net@BigAl> for ; Thu, 15 Jul 2004 10:57:24 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: New Scoop Date: Thu, 15 Jul 2004 07:57:48 -0700 Message-ID: <000001c46a7c$181a6b10$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C46A41.6BBB9310" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C46A41.6BBB9310 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Finally, there has been considerable talk here, in the past, regarding the relationship between the intake size and the radiator area; there have been fewer about the relationship of the outlet size. You have heated air exiting your heat exchangers, that means it's expanding. You need enough outlet area to keep from bottlenecking the airflow _after_ the rad, or you'll lose pressure differential right when you need it the most. That outlet area has to take into account ALL the sources that are adding heat to it - engine radiation, exhaust ... My tupence, Dale R. We have good ol' Charles law that says the expansion is directly proportional to the absolute temperature change. Roughly, we may have an increase in the air temp of maybe 50 - 70 degrees F. So if it is coming in at 80F (533R), the expansion ratio is only about 1.12. Typically we would like the radiator area to at least 3-4 times the inlet area to slow the air to recover pressure and reduce drop across the core. We'd then like to accelerate the air again before it exits; at something near the free-stream velocity. Because of other losses, like sudden expansions at rad exit, or whatever; we don't have good enough conservation of energy to get back up to full speed, so we need exit area greater than 1.12 time the inlet. A rough rule of thumb might be a ratio of about 1.5. And, of course, be sure to include all the inlet and outlet areas. Al ------=_NextPart_000_0001_01C46A41.6BBB9310 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Finally, there has been considerable talk here, in the =

past, regarding the relationship between the intake size

and the radiator area; there have been fewer about the

relationship of the outlet size. You have heated air

exiting your heat exchangers, that means it's expanding. =

You need enough outlet area to keep from bottlenecking

the airflow _after_ the rad, or you'll lose pressure

differential right when you need it the most. That outlet

area has to take into account ALL the sources that are

adding heat to it - engine radiation, exhaust ...

My tupence,

Dale R.

We have good ol’ Charles law that says the = expansion is directly proportional to the absolute temperature change. = Roughly, we may have an increase in the air temp of maybe 50 – 70 degrees = F. So if it is coming in at 80F (533R), the expansion ratio is only about = 1.12.

<= /font>

Typically we = would like the radiator area to at least 3-4 times the inlet area to slow the = air to recover pressure and reduce drop across the core. We’d then = like to accelerate the air again before it exits; at something near the = free-stream velocity. Because of other losses, like sudden expansions at rad exit, or = whatever; we don’t have good enough conservation of energy to get back up to = full speed, so we need exit area greater than 1.12 time the inlet. A = rough rule of thumb might be a ratio of about 1.5. And, of course, be = sure to include all the inlet and outlet areas.

<= /font>

Al

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