X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 17 Jan 2012 11:41:36 -0500 Message-ID: X-Original-Return-Path: Received: from nschwmtas02p.mx.bigpond.com ([61.9.189.140] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTP id 5352708 for lml@lancaironline.net; Mon, 16 Jan 2012 19:48:37 -0500 Received-SPF: pass receiver=logan.com; client-ip=61.9.189.140; envelope-from=frederickmoreno@bigpond.com Received: from nschwcmgw06p ([61.9.190.166]) by nschwmtas02p.mx.bigpond.com with ESMTP id <20120117004801.OKRI391.nschwmtas02p.mx.bigpond.com@nschwcmgw06p> for ; Tue, 17 Jan 2012 00:48:01 +0000 Received: from Razzle ([58.165.11.246]) by nschwcmgw06p with BigPond Outbound id NQnx1i00L5JWv5W01Qo068; Tue, 17 Jan 2012 00:48:01 +0000 X-Authority-Analysis: v=2.0 cv=asYw+FlV c=1 sm=1 a=Ap2HPOVkqcVN/0SrKbfd8g==:17 a=AnaCDbUALDMA:10 a=JDadKst33uMA:10 a=kj9zAlcOel0A:10 a=28e-_nKMqLKXYSa64hAA:9 a=CjuIK1q_8ugA:10 a=VrnVJIGNduSbSBoCc1cA:9 a=6LQEbfqDFdwLIgxMRLYA:7 a=Ap2HPOVkqcVN/0SrKbfd8g==:117 MIME-Version: 1.0 X-Original-Message-Id: <4F14C532.000018.03988@RAZZLE> X-Original-Date: Tue, 17 Jan 2012 08:47:46 +0800 Content-Type: Multipart/Alternative; charset="us-ascii"; boundary="------------Boundary-00=_MJ3XJDU1VA4000000000" X-Mailer: IncrediMail (6244788) From: "Frederick Moreno" X-FID: FLAVOR00-NONE-0000-0000-000000000000 X-Priority: 3 X-Original-To: "Lancair Mail (lml@lancaironline.net)" Subject: Fw: Re: [LML] Re: Ceramic exhaust coatings - careful y'all --------------Boundary-00=_MJ3XJDU1VA4000000000 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Colyn wrote: =0D =0D "That data makes it pretty clear. =0D I had a mechanical engineer/metallurgist friend who was a pilot at one po= int His comment on the equipment was "Airplanes barely work. Helicopters = don t work" I think this exhaust situation is an example of "barely work". = =20 Those margins are really thin.=0D =0D =0D So does this also mean that it is better to paint stainless black than le= ave it shiny?"=0D =0D No. =0D =0D 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 vi= a radiation) of nearly 1.0 making it approach a theoretically perfect infra= red emitter. Leaving it alone and letting nature take its course works just fine. =0D =0D And just to warn folks: what is "non- black" to your eye may be "black" i= n the infrared red. Things that look white in visible light are frequentl= y varying shades of black (emitters or absorbers) in the infra red. =0D =0D 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 co= ol in the sun. =0D =0D But the white paint re-radiates in the infrared efficiently. Thermal analysis in sunlight is a different kettle of fish from hot engine parts.= =20 For exhaust pipes and engine compartments, naturally black pipes are good= , and silvery surfaces to reflect the heat dumped from the pipes are also g= ood Hence the recommendation for shiny aluminumized fabrics to line the ins= ide of the cowl. =0D =0D Fred=0D =0D =0D =0D =20 --------------Boundary-00=_MJ3XJDU1VA4000000000 Content-Type: Text/HTML; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Colyn wrote:

"That data makes it pretty clear.

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

So does this also mean that it is better to paint stainless black th= an 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 he= at via radiation) of nearly 1.0 making it approach a theoretically perfec= t infrared emitter. Leaving it alone and letting nature take i= ts 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 absorbe= rs) in the infra red.

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

But the white paint re-radiates in the infrared efficiently. T= hermal 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 dumpe= d 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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