Return-Path: Received: from bewersdorff.com ([192.220.83.90] verified) by logan.com (CommuniGate Pro SMTP 4.1.6) with SMTP id 2706777 for flyrotary@lancaironline.net; Sun, 02 Nov 2003 13:34:25 -0500 Received: (qmail 33574 invoked by uid 21338); 2 Nov 2003 18:34:21 -0000 Received: from unknown (HELO rapunzel) ([216.101.149.124]) (envelope-sender ) by 192.220.83.90 (qmail-ldap-1.03) with SMTP for ; 2 Nov 2003 18:34:21 -0000 From: "Marko Bewersdorff" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Re: radiator at cowl outlet? Date: Sun, 2 Nov 2003 10:29:54 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0078_01C3A12C.412FCAF0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0078_01C3A12C.412FCAF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit MessageI kind of agree with Ed with the following added thought: I think the difference might be that in general preheated air that took heat from engine block already, means that energy has to not be disposed off by the radiators - good. Adding heat from the exhaust on the other hand is additional energy that doesn't really need to be disposed off - not so good. The turbo and exhaust surface area might be only one square foot or two but the absolute temperature of e.g. 1600F (2060R) versus a 220F radiator (670R) shows that there is a large potential for heat disposal into the airstream. Marko -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On Behalf Of Ed Anderson Sent: Sunday, November 02, 2003 7:23 AM HI Rusty, Been think (always a bad idea in my case) about your concern of heating the air before the radiator (if installed in the outflow area). While there is no question there would be some heating by such things as the turbo, etc. I am not certain that it would significantly effect the air temperature, particularly in flight. Heres what my rational is based on. A single GM evaporator core that we use calculates out to having approx 7000 square inches (actually a bit more) of surface area (fins and tubes) thats approx 48 square feet of surface area for one core. From whats been reported the air temp rise through a core is approx 20-30F getting rid of all the coolant heat the engine needs to have rejected Now you wouldn't want air 30F higher than ambient going into your rear mounted radiator, but I'll bet if you estimated the surface area of your turbo and other significant heat generators that you won't come up with anywhere near 48 square feet. Furthermore if you shield the worst heat producer (your turbo and exhaust), I would imagine you might find your air temp not increasing that much before it reaches your radiator. I intitially was concerned about the same type of thing. I felt that if I ducted the rear of my radiators to my side louvers that would keep the hot air from "reheating" the engine. Well, it seemd to actually make matters worst (I suspect the ducts were restricting the expanding hot air coming out of the radiators). Tracy Crook convinced me that the additional heat content (as opposed to temperature) blowing over the engine was insignificant in adding to the heat load. Removed the outlet ducts and overall cooling improved. So if you do add ducts to get the air from your inlet to the rear, just try to make certain that the ducts help rather than hurt. No calculations, just a gut feeling which of course could be incorrect. Ed Anderson ------=_NextPart_000_0078_01C3A12C.412FCAF0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
I kind=20 of agree with Ed with the following added thought:
I=20 think the difference might be that in general preheated air that = took heat=20 from engine block already, means that energy has to not be = disposed=20 off by the radiators - good. Adding heat from the exhaust on the other = hand is=20 additional energy that doesn't really need to be disposed off - not so=20 good.
The=20 turbo and exhaust surface area might be only one square foot or = two but the=20 absolute temperature of e.g. 1600F (2060R) versus a 220F radiator = (670R)=20 shows that there is a large potential for heat disposal into the=20 airstream.
Marko
 
 
-----Original Message-----
From: Rotary motors in = aircraft=20 [mailto:flyrotary@lancaironline.net]On Behalf Of Ed=20 Anderson
Sent: Sunday, November 02, 2003 7:23 = AM
 
 
HI=20 Rusty,
 
    Been = think (always=20 a bad idea in my case) about your concern of heating the air before = the=20 radiator (if installed in the outflow area).  While there is no = question there would be some heating by such things as the turbo, = etc. =20 I am not certain that it would significantly effect the air = temperature,=20 particularly in flight.
 
Heres what my rational is = based=20 on.  A single GM evaporator core that we use calculates out to = having=20 approx 7000 square inches (actually a bit more) of surface area = (fins=20 and tubes) thats approx  48 square feet of surface area for one = core.  From whats been reported the air temp rise =  through a=20 core is approx 20-30F getting rid of all the coolant heat the engine = needs=20 to have rejected
 
Now you wouldn't want air = 30F higher=20 than ambient going into your rear mounted radiator, but I'll bet if = you=20 estimated the surface area of your turbo and other significant heat=20 generators that you won't come up with anywhere near 48 square = feet. =20 Furthermore if you shield the worst heat producer (your turbo and = exhaust),=20 I would imagine you might find your air temp not increasing that = much before=20 it reaches your radiator. 
 
I intitially was concerned = about the=20 same type of thing.  I felt that if I ducted the rear of my = radiators=20 to my side louvers that would keep the hot air from "reheating" the=20 engine.  Well, it seemd to actually make matters worst (I = suspect the=20 ducts were restricting the expanding hot air coming out of the=20 radiators).  Tracy Crook convinced me that the additional heat = content=20 (as opposed to temperature) blowing over the engine was = insignificant in=20 adding to the heat load.  Removed the outlet ducts and overall = cooling=20 improved.
 
So if you do add ducts to = get the air=20 from your inlet to the rear, just try to make certain that the ducts = help=20 rather than hurt.
 
No calculations, just a = gut feeling=20 which of course could be = incorrect.
 
Ed=20 = Anderson
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