Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2891786 for flyrotary@lancaironline.net; Mon, 15 Dec 2003 12:27:44 -0500 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id hBFHReHH026041 for ; Mon, 15 Dec 2003 12:27:41 -0500 (EST) Message-ID: <000801c3c330$51d3fe00$1702a8c0@WorkGroup> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: evap core versus radiator Date: Mon, 15 Dec 2003 12:24:38 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0005_01C3C306.689940C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0005_01C3C306.689940C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Al, I have 7/8" ID lines (AN-16 hose) plumbed to both with similar = fittings which are about the largest that I could put on the cores. I = fully agree that there are a number of variables that can determine = whether a system is successful or not. It only takes a bit of a = difference between two installations to make one successful and the = other not so successful. =20 Having gone through my flight test phase with marginal cooling, I agree = with your approach, a little too much cooling (if there is such a thing) = won't hurt you and is easy to retify, too little cooling can hurt and is = harder to fix. You are also exploring a bit different regime with your = three rotors, certainly more heat to dump and perhaps other variables = are different as well. So in your case, I would not consider GM cores = to be the best approach. At a miminum, I would think you would need = three of them, which would prepresent a physical configuration challenge = at the least. So I think your route of the custome radiator was a = prudent one. Also, it is sometimes the case that the real cause of overheating it not = what you think. While I initially though I had coolant system and oil = system over heating problems, it turned out it was really the lack of = adqequate oil cooling that was the core problem. Bleed over of heat = that the oil cooler was not dumping was picked up by the coolant system = and was causing elevated coolant temps. =20 Once I solved my oil temp problems, the coolant overheating problem went = away. So they do seem to interact a bit more on the rotary, probably = because over 1/3 of the waste heat is dumped by the oil cooler, so if = its only 70% effective, then the other 30% has to be taken care of by = the coolants system - which might not be able to handle it. I found a source for Kuchemann and Weber's book Aerodynamics of = Propulsion, which I hope I get before Christmas. I have an excerprt of = Chapter 12, and it can get a bit confusing as they are not as careful = about some the designation of some of their various coefficients as I = would have liked. But , all in all about the best theortical text I've = found (that I could almost understand). So far I've identified 7-8 = different coefficients that characterize the phenomona that causes each = pressure-drop or losses in just the air side of a heat exchanger system. = These factos include losses associated with:. Inlet area, Duct/Diffuser Walls, Duct Angle, inlet/core size = ratio,Cooler Core pressure drop, Cooler core heating effect, cooler core = passage exit loss, and rear exit duct size. What I have found most useful from the chapter is the relationship = between pressure drop across the core and maximum heat transfer. = Sometimes folks think that maximum pressure drop equates to maximum = cooling and of course, that is not necessarily the case. The maximum = pressure drop would be caused if the core was a solid block - but, = clearly that would be the worst case for cooling because the air mass = flow would be zero. As best as I can tell at this point, there is an equation in the chapter = that reveals the optimum pressure drop/Mass flow balance between = pressure across the core and air mass through the core. I am working on = trying to see if I can understand it well enough to program it into a = spreadsheet to see what it would indicate about GM cores and other types = of radiators. By, the way, Al how is your project coming? Any forecast completion = dates? Ed .=20 Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Monday, December 15, 2003 11:09 AM Subject: [FlyRotary] Re: evap core versus radiator I fly with two in series and have more than adquate cooling for most = regimes of flight. A steep full power climbout on a hot day will push = the system to its limits, but otherwise they work just fine for the = power an NA 13B is likely to produce. =20 Ed; I certainly wouldn't argue with what works. What size lines and = connectors are you using? I tend to try to err on the side of too much cooling; and may have in = my setup. There are a number of variables we don't really have a good = handle on until we go fly, and it's not a limitation I want to have to = deal with. Al ------=_NextPart_000_0005_01C3C306.689940C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Al, I have 7/8" ID lines (AN-16 hose) = plumbed to=20 both with similar fittings which are about the largest that I could put = on=20 the cores.  I fully agree that there are a number of variables = that=20 can determine whether a system is successful or not. It only takes = a bit of=20 a difference between two installations to make one successful and the = other not=20 so successful. 
 
Having gone through my flight test = phase with=20 marginal cooling, I  agree with your approach, a little too much = cooling=20 (if there is such a thing) won't hurt you and is easy to retify, too = little=20 cooling can hurt and is harder to fix.  You are also exploring = a bit=20 different regime with your three rotors, certainly more heat to dump and = perhaps=20 other variables are different as well.  So in your case, I would = not=20 consider GM cores to be the best approach.  At a miminum, I would = think you=20 would need three of them, which would prepresent a physical = configuration=20 challenge at the least.  So I think your route of the custome = radiator was=20 a prudent one.
 
Also, it is sometimes the case that the = real cause=20 of overheating it not what you think.  While I initially though I = had=20 coolant system and oil system over heating problems, it turned out it = was really=20 the lack of adqequate oil cooling that was the core problem.  Bleed = over of=20 heat that the oil cooler was not dumping was picked up by the coolant = system and=20 was causing elevated coolant temps. 
 
Once I solved my oil temp problems, the = coolant=20 overheating problem went away.  So they do  seem to interact a = bit=20 more on the rotary, probably because over 1/3 of the waste heat is = dumped=20 by the oil cooler, so if its only 70% effective, then the other 30% has = to be=20 taken care of by the coolants system - which might not be able  to = handle=20 it.
 
I found a source for Kuchemann and = Weber's book=20 Aerodynamics of Propulsion, which I hope I get before Christmas.  I = have an=20 excerprt of Chapter 12, and it can get a bit confusing as they are not = as=20 careful about some the designation of some of their various coefficients = as I=20 would have liked.  But , all in all about the best theortical text = I've=20 found (that I could almost understand).  So far I've identified 7-8 = different coefficients that characterize the phenomona that causes each=20 pressure-drop or losses in just the air side of a heat exchanger=20 system.  These factos include losses associated = with:.
 
Inlet area, Duct/Diffuser Walls, Duct = Angle,=20 inlet/core size ratio,Cooler Core pressure drop, Cooler = core heating=20 effect, cooler core passage exit loss, and rear exit duct = size.
 
What I have found most useful from the = chapter is=20 the relationship between pressure drop across the core and maximum heat=20 transfer.  Sometimes folks think that maximum pressure drop equates = to=20 maximum cooling and of course, that is not necessarily the case.  = The=20 maximum pressure drop would be caused if the core was a solid block - = but,=20 clearly that would be the worst case for cooling because the air mass = flow would=20 be zero.
 
As best as I can tell at this point, = there is an=20 equation in the chapter that reveals the optimum pressure drop/Mass flow = balance=20 between pressure across the core and air mass through the core.  I = am=20 working on trying to see if I can understand it well enough to program = it into a=20 spreadsheet to see what it would indicate about GM cores and other types = of=20 radiators.
 
 
By, the way, Al how is your = project=20 coming?  Any forecast completion dates?
 
Ed
 
.
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Monday, December 15, 2003 = 11:09=20 AM
Subject: [FlyRotary] Re: evap = core versus=20 radiator

I fly with two = in series and=20 have more than adquate cooling for most regimes of flight.  A = steep full=20 power climbout on a hot day will push the system to its limits, but = otherwise=20 they work just fine for the power an NA 13B is likely to = produce. =20

 

Ed;

 

I = certainly=20 wouldn=92t argue with what works.  What size lines and connectors = are you=20 using?

I tend to = try to=20 err on the side of too much cooling; and may have in my setup. =  There are=20 a number of variables we don=92t really have a good handle on until we = go fly,=20 and it=92s not a limitation I want to have to deal = with.

 

Al

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