X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 03 Feb 2012 11:14:32 -0500 Message-ID: X-Original-Return-Path: Received: from imr-db03.mx.aol.com ([205.188.91.97] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5381419 for lml@lancaironline.net; Fri, 03 Feb 2012 09:48:17 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.91.97; envelope-from=Sky2high@aol.com Received: from mtaomg-mb01.r1000.mx.aol.com (mtaomg-mb01.r1000.mx.aol.com [172.29.41.72]) by imr-db03.mx.aol.com (8.14.1/8.14.1) with ESMTP id q13ElZC1012642 for ; Fri, 3 Feb 2012 09:47:35 -0500 Received: from core-mtb004a.r1000.mail.aol.com (core-mtb004.r1000.mail.aol.com [172.29.234.205]) by mtaomg-mb01.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 4AAE2E000096 for ; Fri, 3 Feb 2012 09:47:35 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <5053.7f716dc6.3c5d4d87@aol.com> X-Original-Date: Fri, 3 Feb 2012 09:47:35 -0500 (EST) Subject: Re: [LML] Re: Cabin heat X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_5053.7f716dc6.3c5d4d87_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:469588384:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d29484f2bf3872e68 --part1_5053.7f716dc6.3c5d4d87_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Gary, et al, There are many ways to skin a cat. I take cabin heatmuff intake air from the lower horizontal baffling aft of the prop flange via a 1.5 in scat tube. There is no restriction on the air that is dumped into the lower cowl if the cabin heat valve is closed. This intake location does not alter the cooling air distribution to the cylinders. Now, let's talk about temperatures. In the colder months, engine cooling is less of a problem because the intake air is cooler and the separate intake for the oil cooler is partially closed to keep the oil temp indication up close to 180. This is cooling neutral. Let's also remember that the pressure in the cockpit is much lower than that in the upper cowl. Thus, there is no problem in getting hot air into the cockpit and I seldom have the heater control fully open when the sun is also helping with keeping the cockpit warm. In the warmer months, a restriction plate is attached to the intake air opening that changes it from the 1.5" to about .6" and, if the cabin heat valve is closed, that lesser amount of air passes through the muff and is dumped in the lower cowl. Thus, no super heating of the pipe surrounded by the muff nor will the muff itself radiate high heat in the lower cowl. This may also allow more of the upper cowl air to be routed over the cylinders to compensate for the warmer cooling air coming in to the upper cowl. The oil cooler intake air door is open wide and the oil contributes to overall engine cooling. This is also cooling neutral. Try not to let the unknown unknowns get ya...... Hmmmmm.... Never mind. Grayhawk PS: A 320 located in the upper midwest and able to experience the extremes of winter and summer (except for this winter). In a message dated 2/3/2012 7:02:59 A.M. Central Standard Time, casey.gary@yahoo.com writes: Peter, What you mention is certainly the "common knowledge" with respect to cabin heat and every plane I've seen since the dawn of (my) time has been configured to route the hot air overboard when the heater is turned off, not shut it off completely as you describe. Will that portion of the exhaust pipe overheat if no air is flowing through the system? I doubt it, but I'm not sure. How much hotter would it get? I don't know, but I'm sure not a lot. After all, the rest of the exhaust system doesn't have deliberate cooling - it just exists in whatever air flow goes around it, and I've never seen any one worry about that. I would think it more likely that the flex hose attached to the heat muff would overheat and fail prematurely. Yes, the air dumped does reduce the air available to cool the engine. I find it ironic that many (including me) go to great trouble to reduce all leakage around the shroud, including the use of RTV sealant, and then ignore the air flow through the heater valve. Maybe I should put a restricter orifice in the "dump" line to reduce, but not eliminate, that air flow. The answer to your question is that I'm not sure anyone knows the answer to your question. Gary Casey From Peter: I am routing my cabin heat hoses and the follwoing was braought to my attention. Presently I take the pressured air from my plenum, than to the heat exchanger mounted on the exhaust and routing the heated air to the valve which I can open for cabin heat or close it. If I close it, the air gets blocked at the valve as I thought it is better to block it rather to dump the heated air to the cowling. Reason for that is that I get the air from the plenum and dumping it to the plenum reduces the available air to cool the engine and reduces the pressure difference between the plenum and the cowling. Now a friend mentioned that I might get a heat blocking at the heat exchanger with undefined consequences. So to say better dump the air to the cowling rather than getting a cracked exhaust. What is your experience / opinion ? Thanks in advance, Peter --part1_5053.7f716dc6.3c5d4d87_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Gary, et al,
 
There are many ways to skin a cat.  I take cabin heatmuff intake = air=20 from the lower horizontal baffling aft of the prop flange via a 1.5 in= scat=20 tube.  There is no restriction on the air that is dumped into the lowe= r=20 cowl if the cabin heat valve is closed.  This intake location doe= s not=20 alter the cooling air distribution to the cylinders.
 
 Now, let's talk about temperatures. In the colder months, engine= =20 cooling is less of a problem because the intake air is cooler and the separ= ate=20 intake for the oil cooler is partially closed to keep the oil temp=20 indication up close to 180.  This is cooling neutral.  Let's= also=20 remember that the pressure in the cockpit is much lower than that in t= he=20 upper cowl.  Thus, there is no problem in getting hot air into the coc= kpit=20 and I seldom have the heater control fully open when the sun is also helpin= g=20 with keeping the cockpit warm.   
 
In the warmer months, a restriction plate is attached to=20 the intake air opening that changes it from the 1.5" to about .6" and,= =20 if the cabin heat valve is closed, that lesser amount of air pass= es=20 through the muff and is dumped in the lower cowl.  Thus, no super heat= ing=20 of the pipe surrounded by the muff nor will the muff itself radiate hi= gh=20 heat in the lower cowl.  This may also allow more of the upper co= wl=20 air to be routed over the cylinders to compensate for the warmer=20 cooling air coming in to the upper cowl.  The oil cooler intake a= ir=20 door is open wide and the oil contributes to overall engine cooling.&n= bsp;=20 This is also cooling neutral.
 
Try not to let the unknown unknowns get ya......
 
Hmmmmm....  Never mind.
 
Grayhawk
 
PS: A 320 located in the upper midwest and able to experienc= e the=20 extremes of winter and summer (except for this=20 winter).    
 
In a message dated 2/3/2012 7:02:59 A.M. Central Standard Time,=20 casey.gary@yahoo.com writes:
=
Peter,
What you mention is certainly the "common knowledge" with respect to= =20 cabin heat and every plane I've seen since the dawn of (my) time has been= =20 configured to route the hot air overboard when the heater is turned off, = not=20 shut it off completely as you describe.  Will that portion of the ex= haust=20 pipe overheat if no air is flowing through the system?  I doubt it, = but=20 I'm not sure.  How much hotter would it get?  I don't know, but= I'm=20 sure not a lot.  After all, the rest of the exhaust system doesn't h= ave=20 deliberate cooling - it just exists in whatever air flow goes around it, = and=20 I've never seen any one worry about that.  I would think it more lik= ely=20 that the flex hose attached to the heat muff would overheat and fail=20 prematurely.  Yes, the air dumped does reduce the air available to c= ool=20 the engine.  I find it ironic that many (including me) go to great= =20 trouble to reduce all leakage around the shroud, including the use of RTV= =20 sealant, and then ignore the air flow through the heater valve.  May= be I=20 should put a restricter orifice in the "dump" line to reduce, but not=20 eliminate, that air flow.  The answer to your question is that I'm n= ot=20 sure anyone knows the answer to your question.
Gary Casey

From Peter:
I am routing my cabin heat hoses and the follwoing was braought to m= y=20 attention.
 
Presently I take the pressured air from my plenum, than to the heat= =20 exchanger mounted on the exhaust and routing the heated air to the valve = which=20 I can open for cabin heat or close it. If I close it, the air gets blocke= d at=20 the valve as I thought it is better to block it rather to dump the heated= air=20 to the cowling. Reason for that is that I get the air from the plenum and= =20 dumping it to the plenum reduces the available air to cool the engine and= =20 reduces the pressure difference between the plenum and the cowling.
 
Now a friend mentioned that I might get a heat blocking at the heat= =20 exchanger with undefined consequences. So to say better dump the air to t= he=20 cowling rather than getting a cracked exhaust.
 
What is your experience / opinion ?
 
Thanks in advance,
 
Peter
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