Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Fri, 10 Oct 2003 09:27:21 -0400 Message-ID: X-Original-Return-Path: Received: from ms-smtp-03.southeast.rr.com ([24.93.67.84] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2631422 for flyrotary@lancaironline.net; Fri, 10 Oct 2003 09:24:35 -0400 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-03.southeast.rr.com (8.12.10/8.12.2) with SMTP id h9ADMBW0014610 for ; Fri, 10 Oct 2003 09:22:12 -0400 (EDT) X-Original-Message-ID: <001001c38f31$545a9d60$1702a8c0@WorkGroup> From: "Ed Anderson" X-Original-To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] solo's & Delta T... no more emergencies X-Original-Date: Fri, 10 Oct 2003 09:20:52 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000D_01C38F0F.CD05D9E0" 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 This is a multi-part message in MIME format. ------=_NextPart_000_000D_01C38F0F.CD05D9E0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Haywire=20 To: Rotary motors in aircraft=20 Sent: Friday, October 10, 2003 2:30 AM Subject: [FlyRotary] solo's & Delta T... no more emergencies Hey Guy's; Well today we had very high winds (30Kts) so we sat on the ground = most of the day watching SNIP What I found was somewhat surprising. I found that the coolant = rads (2 Ford evap cores plumbed in parallel) had a delta T of 20C, while = the Oil cooler only had a delta T of 5C. SNIP The oil cooler is a little disappointing to have only a Delta T of = 5C or 9F. I'd expected much higher. Ed were you planning on measuring = deltaT through the oil as well or just the coolant? I'd like to know = what others are getting. I hope to get out again tomorrow afternoon and = if the weather is better with higher ceilings, I'll do a longer climb = followed by a longer run at cruise speed to allow temps to stabilize a = little better. Tonight's circuits were admittedly not the ideal run for = gathering data, but I thought some may be interested in my results. I'll = try to gather more data in the days to come.=20 The EWP continues to function perfectly. S. Todd Bartrim Turbo 13B RV-9Endurance C-FSTB =20 Thanks for the data, Todd. I use a delta T of 20F for coolant drop across the GM cores as an = estimate for my cooling calculations. I had not thought about the oil = cooler, but it would be fairly simple matter to just switch a couple of = the thermocouples. I'll put that on my list of "to dos" I wouldn't worry too much about the oil delta T only being 9F so long = as your oil out of your cooler stays below 210F (180F being ideal). I = suspect that the flow rate through the oil cooler is higher (Lynn do = you have figures on the GPM for the oil pump - or anybody?) - which = would mean more heat removed from the engine even with the smaller delta = T.=20 Q =3D M*(Tout-Tin)*Cp, the heat transfer equation indicates that = the heat removed (Q) is dependent on mass flow (M) and Delta = T(Tout-Tin). Specific heat (CP) is fixed for the cooling medium. (One = implicit assumption is that the mass flow (air/water/oil) is carrying = away as much heat as it theoretically can - not always the case in the = real world as things like boundary layers, laminar flow, etc can reduce = the theoretical transfer of heat to the medium) In any case, Q will remain the same so long as the product of = M*(Tout-Tin) remains the same. So if M is less - then the Delta T would = need to be higher (better transfer of heat to the medium), if M is more = then the Delta T can be less for the same amount of Q removed. So while = you can get a greater Delta T by slowing the coolant flow through the = radiator, that means you have decreased M - which means less heat = removal (Q) from the engine. For a given Delta T, the equation shows = you always remove more heat with increase mass flow (M) (all else being = equal). So the 36F is certainly greater than the 20F. Now, the question is = whether that 36F means the system is cooling better? I would say based = on the flow rates you got when experimenting the answer is definitely - = yes. However, as just stated, just because you get a greater Delta T in = coolant temp across the radiators does not Necessarily mean you have = better cooling. =20 While it is always possible to show a greater Delta T by slowing the = flow of coolant through a radiator (exposing it to the cooling air = longer), the crucial cooling performance factor is how much heat (Q) is = being removed from the engine. If the flow (M) is too low, clearly you = impede heat removal from the engine no matter what the Delta T is across = the radiators. It would appear there is an optimum flow rate factor. If its too = slow the delta T across the radiators looks great - but, the slower = cooling flow does not remove as much heat from the engine. It appears = that more flow always results in more heat removed from the engine - = however, above certain flow rates, you start to encounter a lot of = losses due to turbulence, friction, etc. and more power is required to = pump the coolant. Since it appears that the flow rates are comparable (I can't recall = for certain, but, I think you found the Ford cores even flowed a bit = better than the GM cores) between the two type cores and if the 36F = represents the delta T for the Ford Vs 20F for the GM cores for the same = flow rate, then you are clearly getting more heat rejection. So, I would say that if your coolant temp coming out of the engine = stays at or near the 180F or less mark, then you are getting close to = optimum cooling. If the coolant temp varies significant from that then = you may need to check things closer. =20 Its great to get this type of data. It could mean me swapping out my = old GM cores for Ford Cores (it would make my Ford Areostar and Windstar = happier {:>)) Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com ------=_NextPart_000_000D_01C38F0F.CD05D9E0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From:=20 Haywire
Sent: Friday, October 10, 2003 = 2:30=20 AM
Subject: [FlyRotary] solo's = & Delta=20 T... no more emergencies

Hey=20 Guy's;
    Well today we had very high winds (30Kts) so we sat on the = ground most=20 of the day watching  SNIP
 
    What I=20 found was somewhat surprising. I found that the coolant rads (2 Ford = evap=20 cores plumbed in parallel) had a delta T of 20C, while the Oil cooler = only had=20 a delta T of 5C.
 SNIP
 
    The oil cooler is a little disappointing to have only a Delta = T of 5C=20 or 9F. I'd expected much higher. Ed were you planning on measuring = deltaT=20 through the oil as well or just the coolant? I'd like to know what = others are=20 getting. I hope to get out again tomorrow afternoon and if the weather = is=20 better with higher ceilings, I'll do a longer climb followed by a = longer run=20 at cruise speed to allow temps to stabilize a little better. Tonight's = circuits were admittedly not the ideal run for gathering data, but I = thought=20 some may be interested in my results. I'll try to gather more data in = the days=20 to come.
    The EWP continues to function perfectly.

S. Todd Bartrim
Turbo 13B=20 RV-9Endurance
C-FSTB
 

Thanks for the data, = Todd.

I use a delta T of 20F for = coolant drop=20 across the GM cores as an estimate for my cooling calculations. I = had not=20 thought about the oil cooler, but it would be fairly simple matter to = just=20 switch a couple of the thermocouples.  I'll put that on my list = of "to=20 dos"

 I wouldn't worry too = much about=20 the oil delta T only being 9F so long as your oil out of your = cooler=20 stays below 210F (180F being ideal).  I suspect that the flow = rate=20 through the oil cooler is higher  (Lynn do you have figures on = the GPM=20 for the oil pump - or anybody?)  - which would mean more = heat=20 removed from the engine even with the smaller delta = T. 

  Q =3D M*(Tout-Tin)*Cp, the heat transfer = equation  indicates=20 that the heat removed (Q) is dependent on mass flow (M) and Delta=20 T(Tout-Tin). Specific heat (CP) is fixed for the cooling=20 medium.  (One implicit assumption is that the mass flow=20 (air/water/oil) is carrying away as much heat as it theoretically can = - not=20 always the case in the real world as things like boundary layers, = laminar=20 flow, etc can reduce the theoretical transfer of heat to the=20 medium)

 In any case, Q will remain the = same so long=20 as the product of M*(Tout-Tin) remains the same.  So if M is less = - then the Delta T would need to be higher (better transfer of = heat to=20 the medium), if M is more then the Delta T can be less for the same = amount of=20 Q removed. So while you can get a greater Delta T by slowing the = coolant flow=20 through the radiator, that means you have decreased M - which means = less heat=20 removal (Q) from the engine.  For a given Delta T, the equation = shows you=20 always remove more heat with increase mass flow (M) (all else being=20 equal).

 So the 36F is = certainly greater=20 than the 20F.  Now, the question is whether that 36F means the = system is=20 cooling better?  I would say based on the flow rates you got when = experimenting the answer is definitely - yes.  However, as just = stated,=20 just because you get a greater Delta T in coolant temp across the = radiators=20 does not Necessarily mean you have better cooling.  =

 While it is always possible to show a greater Delta T by = slowing the=20 flow of coolant through a radiator (exposing it to the cooling air = longer),=20 the crucial cooling performance factor is how much heat (Q) =  is=20 being removed from the engine. If the flow (M) is too low, = clearly=20 you impede heat removal from the engine no matter what the Delta T is = across=20 the radiators.

 It would appear there is an = optimum flow rate=20 factor.  If its too slow the delta T across the radiators looks = great -=20 but, the slower cooling flow does not remove as much heat = from the=20 engine.  It appears that more flow always results in more heat = removed=20 from the engine - however, above certain flow rates, you start to = encounter a=20 lot of losses due to turbulence, friction, etc. and more power is = required to pump the coolant.

Since it appears that the flow rates = are comparable=20 (I can't recall for certain, but, I think you found the Ford cores = even flowed=20 a bit better than the GM cores) between the two type cores and if the = 36F=20 represents the delta T for the Ford Vs 20F for the GM cores for the = same flow=20 rate, then you are clearly getting more heat rejection.

So, I would say that if your coolant = temp coming=20 out of the engine stays at or near the 180F or less mark,  then = you are=20 getting close to optimum cooling.  If the coolant temp varies = significant=20 from that then you may need to check things closer. 

Its great to get this type of = data.  It could=20 mean me swapping out my old GM cores for Ford Cores (it would make my = Ford=20 Areostar and Windstar happier {:>))

 

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews,=20 NC
eanderson@carolina.rr.com

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