X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.2.2) with ESMTP id 2880849 for flyrotary@lancaironline.net; Thu, 01 May 2008 20:05:03 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=eanderson@carolina.rr.com Received: from edward2 ([75.191.186.236]) by cdptpa-omta02.mail.rr.com with SMTP id <20080502000425.WLH1070.cdptpa-omta02.mail.rr.com@edward2> for ; Fri, 2 May 2008 00:04:25 +0000 Message-ID: <001801c8abe8$17ff5170$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: radiator orientation? Date: Thu, 1 May 2008 20:04:29 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0015_01C8ABC6.90AD4D10" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 This is a multi-part message in MIME format. ------=_NextPart_000_0015_01C8ABC6.90AD4D10 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable You are correct, Mark, Minimizing or eliminating laminar flow next to = metal - in other words causing the laminar flow in the boundary layer to = become turbulence does promote heat transfer. It also increase skin = friction and drag. However, if the turbulence gets to the point of = causing air flow separation then that hurts both cooling and the drag = factor. So like most other things involving aircraft - compromise is = called for. My cores are slanted - but, only because I could not fit them in the = space I had allocated for them any other way. Otherwise they would be = perpendicular to the air flow. Clearly slanted cores do work and most = of the time we install them in that orientation due to space constraints = or aesthetics as Pat Panzera indicated in his response. If you use the Streamline duct approach to the duct design for a = perpendicular core, it is easier to plot the coordinates and fabricate = the duct - in my opinion. My duct lengths are approx 3 1/2" on the = short side and 6" on the long side making for a very short duct indeed.=20 However, I keep the duct cross sectional small until just before the = core and then permit it to balloon into the bell or trumpet shape of the = streamline duct. This delays air flow separation and the pressure = recovery (according to the theory) that causes it - until the last = moment. Separation does occur but it occurs up in the corners where it = has minimal impact on air flow through most of the core. In fact, the = streamline duct equation even indicates at what angle of divergence of = the flare causes separation. It varies depending on the size of opening = and size of core/ratio - but, generally the separation occurs above 65 = deg of divergence and in some cases into 75 deg. Some would disagree with this approach, but I have flow with it for = years now and my cooling system appears close to optimum for my set up = with minimum excessive cooling capacity and drag. Your milage may vary = of course (doesn't it always {:>))? Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.dmack.net/mazda/index.html From: Mark Steitle=20 To: Rotary motors in aircraft=20 Sent: Thursday, May 01, 2008 7:45 PM Subject: [FlyRotary] Re: radiator orientation? Ed,=20 But doesn't "creating turbulence" improve heat exchanger efficiency? = I thought that was why they put corrugated fins on the cores. =20 Mark S. On Thu, May 1, 2008 at 6:38 PM, Ed Anderson = wrote: Michael, My view is that slanting a radiator does nothing better for you than = one perpendicular to the air flow - except perhaps making it easier to = fit a space constraint, it which case then go with a slanted radiator. A slanted radiator (that has the same air flow and same frontal = area) as a perpendicular radiator is actually added going to have a bit = more drag. The air flow must now make at least one (and possibly two = turns) going into and out of the core channels creating turbulence and = drag at those points. NOT that it is going to make a real significant = difference at the airspeeds we fly. So for that reason, a slanted = radiator is certainly acceptable especially to meet installation = constraints. My 0.02 Ed ----- Original Message ----- From: "Michael Silvius" = To: "Rotary motors in aircraft" Sent: Thursday, May 01, 2008 8:10 PM Subject: [FlyRotary] Re: radiator orientation? Geroge: In the end I will likely angle them a bit but my primary concern = is if it is ok to install these radiators in the vertical orientation. I have = the space up and down to use them this way. The nose bowl I have seems to = work well with things set up that way. Michael ----- Original Message ----- From: "George Lendich" = To: "Rotary motors in aircraft" Sent: Thursday, May 01, 2008 5:50 PM Subject: [FlyRotary] Re: radiator orientation? > Anyonene see any issues of concern with instaling the = radiators in the > vertical orientation as oposed to their normal orientation = with the inlets > and outlet on the top. These are evaporator cores from a JMC = Jimmy- Chevy > Blazer > > Michael in Maine Michael, The front adds significantly to the flat plate drag and anything = you can do to reduce that affects the total drag. Are you happy with the = front width, could it be reduced with some angle on the rads? George ( down under) -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0015_01C8ABC6.90AD4D10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
You are correct, Mark, Minimizing or = eliminating=20 laminar flow next to metal - in other words causing the laminar flow in = the=20 boundary layer to become turbulence does promote heat transfer.  It = also=20 increase skin friction and drag.  However, if the turbulence gets = to the=20 point of causing air flow separation then that hurts both cooling and = the drag=20 factor.  So like most other things involving aircraft - compromise = is=20 called for.
 
My cores are slanted - but, only = because I could=20 not fit them in the space I had allocated for them any other way. =20 Otherwise they would be perpendicular to the air flow.  Clearly = slanted=20 cores do work and most of the time we install them in that orientation = due to=20 space constraints or aesthetics as Pat Panzera indicated in his=20 response.
 
If you use the Streamline duct approach = to the=20 duct design for a perpendicular core, it is easier to plot the = coordinates and=20 fabricate the duct - in my opinion.  My duct lengths are approx =  3=20 1/2" on the short side and 6" on the long side making for a very short = duct=20 indeed. 
 
 However, I keep the duct cross = sectional=20 small until just before the core and then permit it to balloon into the = bell or=20 trumpet shape of the streamline duct.  This delays air flow = separation and=20 the pressure recovery (according to the theory) that causes it = - until=20 the last moment.  Separation does occur but it occurs up in the = corners=20 where it has minimal impact on air flow through most of the core.  = In fact,=20 the streamline duct equation even indicates at what angle of divergence = of the=20 flare causes separation.  It varies depending on the size of = opening and=20 size of core/ratio - but, generally the separation occurs above 65 deg = of=20 divergence and in some cases into 75 deg.
 
Some would disagree with this approach, = but I=20 have flow with it for years now and my cooling system appears close to = optimum=20 for my set up with minimum excessive cooling capacity and drag.  = Your=20 milage may vary of course (doesn't it always {:>))?
 
 
Ed
Ed Anderson
Rv-6A N494BW Rotary=20 Powered
Matthews,=20 NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://me= mbers.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda= /index.html
 
From:=20 Mark = Steitle=20
Sent: Thursday, May 01, 2008 = 7:45=20 PM
Subject: [FlyRotary] Re: = radiator=20 orientation?

Ed,

But doesn't "creating turbulence" improve = heat=20 exchanger efficiency?   I thought that was why they put = corrugated=20 fins on the cores. 

Mark S.


On Thu, May 1, 2008 at 6:38 PM, Ed Anderson = <eanderson@carolina.rr.com&g= t;=20 wrote:
Michael,

My=20 view is that slanting a radiator does nothing better for you than = one=20 perpendicular to the air flow - except perhaps making it easier to = fit a=20 space constraint, it which case then go with a slanted = radiator.

A=20 slanted radiator (that has the same air flow and same frontal area) = as a=20 perpendicular radiator  is actually added going to have a bit = more=20 drag. The air flow must now make at least one (and possibly two = turns) going=20 into and out of the core channels creating turbulence and drag at = those=20 points. NOT that it is going to make a real significant difference = at the=20 airspeeds we fly.  So for that reason, a slanted radiator is = certainly=20 acceptable especially to meet installation constraints.

My=20 0.02

Ed




----- Original Message ----- From: = "Michael Silvius" <silvius@gwi.net>
To: "Rotary motors in = aircraft"=20 <flyrotary@lancaironline.net>
Sent: = Thursday, May 01,=20 2008 8:10 PM
Subject: [FlyRotary] Re: radiator = orientation?


Geroge:

In=20 the end I will likely angle them a bit but my primary concern is = if it=20 is
ok to install these radiators in the vertical orientation. I = have=20 the space
up and down to use them this way. The nose bowl I = have seems=20 to work well
with things set up that=20 way.

Michael




----- Original Message = ----- From:=20 "George Lendich" <lendich@optusnet.com.au>
To: "Rotary = motors in=20 aircraft" <flyrotary@lancaironline.net>
Sent: = Thursday, May=20 01, 2008 5:50 PM
Subject: [FlyRotary] Re: radiator=20 orientation?



>=20 Anyonene see any issues of concern with instaling the radiators = in=20 the
> vertical orientation as oposed to their normal = orientation=20 with the
inlets
>=20 and outlet on the top. These are evaporator cores from a JMC=20 Jimmy-
Chevy
>=20 Blazer
>
> Michael in Maine

Michael,
The = front=20 adds significantly to the flat plate drag and anything you=20 can
do
to=20 reduce that affects the total drag. Are you happy with the front = width,
could it be reduced with some angle on the = rads?
George (=20 down under)


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