Return-Path: Received: from imo-d22.mx.aol.com ([205.188.144.208] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 854186 for flyrotary@lancaironline.net; Mon, 04 Apr 2005 10:49:49 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.144.208; envelope-from=Shearbond@aol.com Received: from Shearbond@aol.com by imo-d22.mx.aol.com (mail_out_v37_r5.33.) id q.9a.23be67df (4116) for ; Mon, 4 Apr 2005 10:48:53 -0400 (EDT) From: Shearbond@aol.com Message-ID: <9a.23be67df.2f82add4@aol.com> Date: Mon, 4 Apr 2005 10:48:52 EDT Subject: Cooling Inlet Areas/Bernie's RV9 To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1112626132" X-Mailer: 9.0 SE for Windows sub 5012 -------------------------------1112626132 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit From my work on Compact Heat Exchangers especially as related to my friend's 13B powered RV-3, Bernie has plenty of heat exchanger "frontal area" and "volume". That said, there are two further considerations in the "gotta have" category to be able to confidently taxi out and T/O WOT for as long as one wants in Military Air (+40 deg F over std.) conditions. First....if cooling air can't get out, it can't get in. That is: adequate air exit area is absolute. The exit area must be sufficient for both coolant and oil cooling exit air. For 200 HP that is about 2.1(oil + coolant + now heated air) x .30 x HP or 2.1 x .30 x 200 = 126 sq. in. total for 200 HP. Yes, that is larger than an air cooled engine would require but investigate the temperature differentials between a 350 deg F air cooled cylinder and a 200 deg F hot coolant and one will quickly realize that there must be more lbs. of air flow for a coolant cooled engine. Second, even if cooling can get out, if it can't get in, it can't be there to cool the heat exchangers. Rule of thumb: 0.3 sq. in. of cowling inlet air opening per HP. 200 HP x .3 = 60 sq. in. Note: This assumes a reasonably shaped inlet cowl which has been discussed online often. IMHO: Berni's plane inlet shape and inlet cowl is fine, but I question his inlet opening area. Note: the exhaust area requirement is greater than the inlet combination of oil and coolant due to the now considerable hotter air temperature. Rule of thumb: Coolant air inlet opening for 200 HP coolant cooled engine ~60 sq. in., oil inlet opening ~30 sq. in. equals a total opening of 90 sq. in. A good place to start with exhaust opening is 1.4 times the inlets or 126 sq. in. Close the exit area down with cowl flaps to as little as 80% of the inlet combination at cruise conditions! Don't mean to start another stream of threads on an old subject, but we sweated over this one for 3 months and 3 systems and one might save a lot of time by comparing ones system to these simple "works great" rules of thumb which are the result of LOTS of technical and experimental work. Doug Dempsey N6415Q and RV7 in process Colorado, USA -------------------------------1112626132 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

From my work on Compact Heat Exchangers especially as related to my=20 friend's 13B powered RV-3, Bernie has plenty of heat exchanger "frontal= =20 area" and "volume".

That said, there are two further considerations in the "gotta have"=20 category to be able to confidently taxi out and T/O WOT for as long as one w= ants=20 in Military Air (+40 deg F over std.) conditions.

First....if cooling air can't get out, it can't get in. That is:=20 adequate air exit area is absolute. The exit area must be sufficient f= or=20 both coolant and oil cooling exit air. For 200 HP that is about 2.1(oi= l +=20 coolant + now heated air) x .30 x HP or 2.1 x .30 x 200 =3D 1= 26 sq.=20 in. total for 200 HP.

Yes, that is larger than an air cooled engine would require but investi= gate=20 the temperature differentials between a 350 deg F air cooled cylinder and a=20= 200=20 deg F hot coolant and one will quickly realize that there must be more lbs.=20= of=20 air flow for a coolant cooled engine.

Second, even if cooling can get out, if it can't get in, it can't=20= be=20 there to cool the heat exchangers. Rule of thumb: 0.3 sq. in. of cowli= ng=20 inlet air opening per HP. 200 HP x .3 =3D 60 sq. in. Note: This=20 assumes a reasonably shaped inlet cowl which has been discussed online=20 often. IMHO: Berni's plane inlet shape and inlet cowl is fin= e,=20 but I question his inlet opening area.

Note: the exhaust area requirement is greater than the inlet= =20 combination of oil and coolant due to the now considerable hotter air=20 temperature. Rule of thumb: Coolant air inlet opening for 200 HP= =20 coolant cooled engine ~60 sq. in., oil inlet opening ~30 sq. in. equals a to= tal=20 opening of 90 sq. in. A good place to start with exhaust opening is 1.= 4=20 times the inlets or 126 sq. in. Close the exit area down with cowl fla= ps=20 to as little as 80% of the inlet combination at cruise conditions!

Don't mean to start another stream of threads on an old subject, but we= =20 sweated over this one for 3 months and 3 systems and one might save a lot of= =20 time by comparing ones system to these simple "works great" rules of thumb w= hich=20 are the result of LOTS of technical and experimental work.

Doug Dempsey

N6415Q and RV7 in process

Colorado, USA

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