X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 17 Jan 2012 12:24:39 -0500 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTP id 5353725 for lml@lancaironline.net; Tue, 17 Jan 2012 12:17:00 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=huLEhcSvkJdHnOkcCqNWxypC/MkgyAIQdTSqV3vTXB0PTAIp51XPbEOJZd/7+Tcr; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [72.73.82.72] (helo=[192.168.1.24]) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1RnCe0-0003P1-Si for lml@lancaironline.net; Tue, 17 Jan 2012 12:16:25 -0500 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: multipart/alternative; boundary=Apple-Mail-121-621032804 Subject: Re: [LML] Fw: Re: [LML] Re: Ceramic exhaust coatings - careful y'all X-Original-Date: Tue, 17 Jan 2012 12:16:23 -0500 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1084) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da94024297932360f48ceb38a60fbd22309e0350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 72.73.82.72 --Apple-Mail-121-621032804 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii so what happens to the pipe if you put a shiny reflector .25 - .5" away = to keep the heat off the cylinder heads? Most of the ones i've seen are concentric to the pipe....which seems = like a bad idea. On Jan 17, 2012, at 11:41 AM, Frederick Moreno wrote: Colyn wrote:=20 =20 "That data makes it pretty clear. I had a mechanical engineer/metallurgist friend who was a pilot at one = point. His comment on the equipment was "Airplanes barely work. = Helicopters don't work" I think this exhaust situation is an example = of "barely work". Those margins are really thin. So does this also mean that it is better to paint stainless black than = leave it shiny?" =20 No. =20 Above 1000-1200F stainless steel turns gray/black on its own due to = oxidation of the chromium. It has an emissivity (ability to dump heat = via radiation) of nearly 1.0 making it approach a theoretically perfect = infrared emitter. Leaving it alone and letting nature take its course = works just fine.=20 =20 And just to warn folks: what is "non- black" to your eye may be "black" = in the infrared red. Things that look white in visible light are = frequently varying shades of black (emitters or absorbers) in the infra = red.=20 =20 Since sunlight radiation peaks in the visible (not a coincidence), your = eyes work well for evaluating what is "black" in sunlight. That is why = the upward-facing surfaces of composite airplanes should be white, to = stay cool in the sun.=20 =20 But the white paint re-radiates in the infrared efficiently. Thermal = analysis in sunlight is a different kettle of fish from hot engine = parts. For exhaust pipes and engine compartments, naturally black = pipes are good, and silvery surfaces to reflect the heat dumped from the = pipes are also good. Hence the recommendation for shiny aluminumized = fabrics to line the inside of the cowl. =20 Fred =20 =20 =20 =20 =20 --Apple-Mail-121-621032804 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii so what happens to the pipe if you put a shiny = reflector .25 - .5" away to keep the heat off the cylinder = heads?

Most of the ones i've seen are concentric to the = pipe....which seems like a bad idea.

On Jan = 17, 2012, at 11:41 AM, Frederick Moreno wrote:

Colyn = wrote:

"That data makes it pretty = clear.

I had a mechanical engineer/metallurgist friend who was = a pilot at one point. His comment on the equipment was "Airplanes = barely work. Helicopters don't work" I think this exhaust = situation is an example of "barely work". Those margins are = really thin.

So does this also mean that it is = better to paint stainless black than leave it = shiny?"

No.

Above = 1000-1200F stainless steel turns gray/black on its own due to oxidation = of the chromium. It has an emissivity (ability to dump heat via = radiation) of nearly 1.0 making it approach a theoretically perfect = infrared emitter. Leaving it alone and letting nature take = its course works just fine.

And just to = warn folks: what is "non- black" to your eye may be "black" in = the infrared red. Things that look white in visible light = are frequently varying shades of black (emitters or absorbers) in the = infra red.

Since sunlight radiation = peaks in the visible (not a coincidence), your eyes work well = for evaluating what is "black" in sunlight. That is why the = upward-facing surfaces of composite airplanes should be white, to stay = cool in the sun.

But the white paint = re-radiates in the infrared efficiently. Thermal analysis in = sunlight is a different kettle of fish from hot engine = parts. For exhaust pipes and engine compartments, naturally = black pipes are good, and silvery surfaces to reflect the heat = dumped from the pipes are also good. Hence the = recommendation for shiny aluminumized fabrics to line the inside of the = cowl.

Fred

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= --Apple-Mail-121-621032804--