X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [66.219.56.245] (HELO mail.qnsi.net) by logan.com (CommuniGate Pro SMTP 6.0c2) with ESMTP id 5850864 for flyrotary@lancaironline.net; Wed, 31 Oct 2012 12:55:59 -0400 Received-SPF: none receiver=logan.com; client-ip=66.219.56.245; envelope-from=bhughes@qnsi.net Content-class: urn:content-classes:message Return-Receipt-To: "Bobby J. Hughes" MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01CDB788.85A1089F" Disposition-Notification-To: "Bobby J. Hughes" Subject: RE: [FlyRotary] Re: flow path in conventional radiator X-MimeOLE: Produced By Microsoft Exchange V6.5 Date: Wed, 31 Oct 2012 11:55:24 -0500 Message-ID: <74120FDE88CAFE4DBDA8814BCE20A3F34721DC@qnsi-mail.qnsi.net> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [FlyRotary] Re: flow path in conventional radiator Thread-Index: Ac23iISlZkQOaARBRCuyTXn68YUI5A== From: "Bobby J. Hughes" To: "Rotary motors in aircraft" This is a multi-part message in MIME format. ------_=_NextPart_001_01CDB788.85A1089F Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable The top cowl area right behind the prop should be low pressure and could provide an extraction effect that increases with angle of attack. I did some limited testing last summer that looked promising. By promising I mean less exit area with no decrease in cooling for my setup. But my bottom exit that was blocked off during the tests may be too large to start with. Fabricating a working cowl flap for that area would be a pain and I will likely close up the holes. I can confirm it helped my ground cooling. =20 One flying example with some data points. http://www.melmoth2.com/texts/Cooling%20flow.htm =20 =20 I have not read PL's book but Tracy is cooling more HP per cubic inch of heat exchanger than anyone I'm aware of. =20 =20 =20 Bobby =20 =20 =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bill Bradburry Sent: Wednesday, October 31, 2012 11:03 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: flow path in conventional radiator =20 Ken, =20 I am not certain that the best places for air entrance and exit on an airplane change much with speed. You need entrances in high pressure areas and exits in low pressure areas. The top of the cowl is a high pressure area and if you try to exit air there, I suspect that it will partially block the flow. =20 While I have heard a lot of good stuff about the Paul Lamar book, I usually try to get my guidance from folks who have actually built an airplane. =20 Bill B =20 ________________________________ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net ] On Behalf Of Kenneth Johnson Sent: Wednesday, October 31, 2012 11:03 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: flow path in conventional radiator =20 Tracy, Sorry to get back to you so late, but am now just getting caught up on emails. When I have free time, I am usually out in my garage working on the plane. If you have not read "How to Cool Your Wankel" by Paul Lamar, I would recommend it. It would be worth your time. =20 =20 The suggestion to flow air from the bottom up was not made by Paul, but was my thoughts regarding the airplane I am building. The Zenith 801 is the four passenger high wing STOL bush-type plane. It's top speed is 110 MPH. It's primary purpose is getting in and out of short, grass strips. Where engine cooling is most needed is on short runway take-off with high obstacles such as trees at the runway's end. Stall speed is about 40 MPH. This just means there is very little air flowing through the cooling system on take-off. The airplane is at a high angle of attack until obstacles are cleared. And again, at this high angle of attack, cooling flow is different and airspeed is slow. Having the cowl opening on the bottom front of the cowl where air flows directly through the radiators and having outlets on the top sides of the cowl would allow air to flow best when it is most needed to cool the engine. At flat and level flying, the air would still flow, but the higher speed would provide more cooling. =20 =20 What makes this plane unique is it is not an RV where one is flying at 170 knots and has a mile long runway. =20 =20 Please read Paul's book and give me your thoughts. Thanks for your comments. =20 =20 Ken Johnson =20 =20 =20 ________________________________ From: Tracy > To: Rotary motors in aircraft >=20 Sent: Wednesday, October 24, 2012 12:21 PM Subject: [FlyRotary] Re: flow path in conventional radiator On Oct 24, 2012, at 10:14 AM, Kenneth Johnson wrote: > A more efficient design would have intake air entering the bottom anterior of the the cowl and to pass through the radiator. As this air is heated by the radiator it rises and should exit the top sides of the cowl. No one has done that because of the risk of engine oil on the windshield. I haven't read Paul's book but if this is an example of his suggestions, I wouldn't have much confidence in it. =20 Two basic rules of thumb for A/C cooling systems are: 1. Turning high speed air is hard to do and loss prone energy wise. 2. The pressure represented by convection of rising hot air is not significant and can safely be ignored for our purposes. =20 Tracy -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html ------_=_NextPart_001_01CDB788.85A1089F Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

The top cowl area right behind the prop should be low pressure and = could provide an extraction effect that increases with angle of = attack. I did some limited testing last summer that looked promising. By = promising I mean less exit area with no decrease in cooling for my = setup. But my bottom exit that was blocked off during the tests may be = too large to start with.  Fabricating a working cowl flap for that = area would be a pain and I will likely close up the holes. I can confirm = it helped my ground cooling.

 

One flying example with some data points. =    http://www.melmoth2.com/texts/Cooling%20flow.htm

 

 

I have not read PL’s book but Tracy is cooling more HP per = cubic inch of heat exchanger than anyone I’m aware of. =  

 

 

Bobby

 

 

 

From:= = Rotary motors in aircraft [mailto:flyrotary@lancaironlin= e.net] On Behalf Of Bill Bradburry
Sent: Wednesday, = October 31, 2012 11:03 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: flow path in conventional = radiator

 

Ke= n,

 

I = am not certain that the best places for air entrance and exit on an = airplane change much with speed.  You need entrances in high = pressure areas and exits in low pressure areas.  The top of the = cowl is a high pressure area and if you try to exit air there, I suspect = that it will partially block the flow.

 

Wh= ile I have heard a lot of good stuff about the Paul Lamar book, I = usually try to get my guidance from folks who have actually built an = airplane.

 

Bi= ll B

 

From:= = Rotary motors in aircraft [mailto:flyro= tary@lancaironline.net] On = Behalf Of Kenneth Johnson
Sent: Wednesday, October 31, = 2012 11:03 AM
To: Rotary motors in aircraft
Subject: = [FlyRotary] Re: flow path in conventional = radiator

 

Tracy,

Sorry to get back to you = so late, but am now just getting caught up on emails.  When I have = free time, I am usually out in my garage working on the plane.  If = you have not read "How to Cool Your Wankel" by Paul Lamar, I = would recommend it.  It would be worth your = time.  

 

The suggestion to flow air = from the bottom up was not made by Paul, but was my thoughts regarding = the airplane I am building.  The Zenith 801 is the four passenger = high wing STOL bush-type plane.  It's top speed is 110 MPH.  = It's primary purpose is getting in and out of short, grass strips.  = Where engine cooling is most needed is on short runway take-off with = high obstacles such as trees at the runway's end.  Stall speed is = about 40 MPH.  This just means there is very little air flowing = through the cooling system on take-off.   The airplane is at a = high angle of attack until obstacles are cleared.  And again, at = this high angle of attack, cooling flow is different and airspeed is = slow.

Having the cowl opening on the bottom front of the = cowl where air flows directly through the radiators and having outlets = on the top sides of the cowl would allow air to flow best when it is = most needed to cool the engine.  At flat and level flying, the air = would still flow, but the higher speed would provide more = cooling.  

 

What makes this plane = unique is it is not an RV where one is flying at 170 knots and has a = mile long runway.   

 

Please read Paul's book = and give me your thoughts.  Thanks for your comments.  =

 

Ken = Johnson

 

 

 

<= hr size=3D1 width=3D"100%" align=3Dcenter>

F= rom: = Tracy <rwstracy@gmai= l.com&= gt;
To: Rotary motors in aircraft <flyrotary@lan= caironline.net&= gt;
Sent: Wednesday, October 24, 2012 12:21 = PM
Subject: [FlyRotary] Re: flow path in conventional = radiator




On Oct 24, 2012, at 10:14 AM, Kenneth = Johnson <kjohnsondds@yahoo.com> wrote:

> A more efficient design = would  have intake air entering the bottom anterior of the the cowl = and to pass through the radiator.  As this air is heated by the = radiator it rises and should exit the top sides of the cowl.  No = one has done that because of the risk of engine oil on the = windshield.


I haven't read Paul's book but if this is an = example of his suggestions, I wouldn't have much confidence in it.  =

Two basic rules of thumb for A/C cooling systems are:

1. = Turning high speed air is hard to do and loss prone energy = wise.

2.  The pressure represented by convection of rising = hot air is not significant  and can safely be ignored for our = purposes. 

Tracy
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