X-Junk-Score: 0 [] X-Cloudmark-Score: 0 [] X-Cloudmark-Analysis: v=2.2 cv=HLeBLclv c=1 sm=1 tr=0 a=n+Rs93tcLv4O8RJuqqIilw==:117 a=GiyOdSQuLXryBG4WGbRkgQ==:17 a=x7bEGLp0ZPQA:10 a=7mUfYlMuFuIA:10 a=ZR5kwuB734kA:10 a=kuH323ycUi0A:10 a=r77TgQKjGQsHNAKrUKIA:9 a=ayC55rCoAAAA:8 a=z8_eoGVJAAAA:8 a=DUUX4chWAet44DYOTPcA:9 a=7YouhH5f2OaIkudq:21 a=sMLPdq157HuMdsf0:21 a=QEXdDO2ut3YA:10 a=4PR2P7QzAAAA:8 a=GcgPUb4UXdv1AXSaaJ8A:9 a=iwk-tkDTOw2JLSZA:21 a=RuJe_aMFstWz7hdL:21 a=YDSlmjIl1QpH7Adb:21 a=_W_S_7VecoQA:10 a=B_RyunTPg8udlmYm5Cu2:22 a=4dqwQCo7Po2mVW515mGf:22 From: "Finn Lassen finn.lassen@verizon.net" Received: from sonic306-30.consmr.mail.bf2.yahoo.com ([74.6.132.229] verified) by logan.com (CommuniGate Pro SMTP 6.2.5) with ESMTP id 11305057 for flyrotary@lancaironline.net; Tue, 26 Jun 2018 13:57:13 -0400 Received-SPF: neutral receiver=logan.com; client-ip=74.6.132.229; envelope-from=finn.lassen@verizon.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s2048; t=1530035799; bh=GYfMFjw1mhAyYszsfsiFnwsFW8EtcoISjijCsaxZv4Q=; h=Subject:To:References:From:Date:In-Reply-To:From:Subject; b=F2R0/4NR0rbl/b+b9JVZeU4VY+jVBWvSfVm2b8gady8eQ4bVKCe1udY1L+h3Q+Sw4nxvNdRwSgqZ/o7c7b3oxbMfVsEVLKFM3+ZGR3PVNPxg46DZAOQOw17k+/+zc/MbLAtvovZ9MvrhuwO2grL+7vb/DDl/5wwjfWAxQ+MBabqv6Y3MkEV8Ia9S/I1HcTMdT3jQt4dIeY+iBKnpDSFKWKGXK+iOD2I4q0u8QWLmHvLYCsHcB4JGZ5vvILXptSJ+KLvXmHYIysDIJJs3g+LNgK/tvhCfIor/VcSyhrhNRNlTbNyJ5w8A/x2jed+0H3izW+UYCn5c4OL4M1ZCHkr/9g== X-YMail-OSG: RQyGY9wVM1kN5K4LERMcyoPvAbtheNONT1vpfuW8m0KxJwjeKXQODPuCJ04_FBw FsNimBLXyvUlBWFp1w1lpa0D96HL1v.3tcf3pOo09yrz8qg-- Received: from sonic.gate.mail.ne1.yahoo.com by sonic306.consmr.mail.bf2.yahoo.com with HTTP; Tue, 26 Jun 2018 17:56:39 +0000 Received: from 234.sub-174-228-132.myvzw.com (EHLO [192.168.1.2]) ([174.228.132.234]) by smtp427.mail.bf1.yahoo.com (Oath Hermes SMTP Server) with ESMTPA ID 9dd95d311b0a36d078ed4d5aab98cc1a for ; Tue, 26 Jun 2018 17:52:37 +0000 (UTC) Subject: Re: [FlyRotary] Re: Oil To: Rotary motors in aircraft References: Message-ID: Date: Tue, 26 Jun 2018 13:52:35 -0400 User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/alternative; boundary="------------2E6E555E933EBD16616EE75C" Content-Language: en-US This is a multi-part message in MIME format. --------------2E6E555E933EBD16616EE75C Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Hi Ed, good to see you on the list. Unincumbered by engineering education when it comes to flows, restrictions and heat transfer I'm free to ponder the subject. I keep thinking about a garden hose laying in the sun for a while. Initially you get hot water, but after a while it gets cold again when you let it run. So I think a number of factors hide in the "cp" factor below. How many of the water/oil molecules get in contact with the walls (engine and cooler) must be a factor. Thus the turbulators in the Mazda oil cooler. Time must also be a factor, at least in terms of letting each molecule move to the wall. So even if increased speed of flow may not hurt, it seems counter intuitive to make water/oil flow so fast that heat transfer does not take place. There must be some kind of bell curve where you have a fluid speed for optimum heat transfer. Actually that curve must be a composite of conditions in the engine and of conditions in the cooler. An additional factor for the cooler is how well the heat is transferred from cooler to air. A cold wall should make heat transfer from fluid to air go that faster? So what kind of instrumentation (measuring points) would enable us to optimize speed of fluid flow? Finn On 6/24/2018 4:36 PM, Ed Anderson eanderson@carolina.rr.com wrote: > You said it well, Ernest > What you want is heat removal from the engine.  Slowing flow down > through a radiator will indeed show a larger Delta T from intake to > outlet because the coolant(in the radiator) is exposed to cooling air > longer.  That has led many to believe erroneously that slow flow = > more heat removal.  I once argued an hour with old man Lou Ross about > this issue and when I told him that the obvious conclusion was that if > slowed water cooled better, then stopped water would cool best – there > was silence on the other end of the phone and then Lou hung up and > never spoke to me again. > Part of the myth also stems the results when attempts were made to > improve flow rate by speeding up the coolant pump expecting better > cooling.  When worst cooling occurred, it was concluded erroneously > that the faster flow resulted in worst cooling. In most if not all of > those instances, the poor cooling resulted from less flow – the faster > water pump was actually cavitating and therefore actually pumping less > coolant than at slower rotating speeds where cavitation did not > occur.  But, it all fed into the myth. > Heat duty (Q): Heat duty is defined as the product of mass flow > rate specific heat capacity and the temperature difference > between inlet and outlet fluid temperatures > Q = m*cp* DT > A rule of thumb regarding heat removal and flow rate is: > /The heat transfer coefficient decreases by ˜10% with a threefold > increase in the mass flow rate/ > // > /reference: https://www.tandfonline.com/doi/abs/10.13182/NT09-A7406/ > // > // > So a 10% decrease in transfer resulting from  three times the mass > flow shows that increased mass flow (in of itself) will result in > increased heat removal even though the heat transfer rate may lessen > slightly. > At some point you get pressure losses and other factors - not to > mention the greatly increased power required to get the large increase > in mass flow - makes it impractical to infinitely increase flow rate.  > Once you get the flow good enough to cool your engine under whatever > the conditions you are operating within, it makes little sense to > waste power to get more flow > However, we want best heat removal from the engine.  Heat is removed > via mass flow of the liquid – no mass flow = no cooling.  So the more > mass flow(within reason) - the more heat is removed from the engine > and provided we can get rid of a certain amount of that heat though > the radiator the more cooling of the engine occurs. So it’s a system, > the cooler the oil returned to the engine the better heat transfer, > the more mass flow from engine to radiator the more cooling, the > cooler the air flowing across the radiator the better the heat > rejection, etc.  All factors contribute and you can not focus on just > one factor, the optimum cooling results from the optimization of all > the major variables involved for a particular situation. > Just my 0.02  Back to my cave > Ed --------------2E6E555E933EBD16616EE75C Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit
Hi Ed, good to see you on the list.

Unincumbered by engineering education when it comes to flows, restrictions and heat transfer I'm free to ponder the subject.

I keep thinking about a garden hose laying in the sun for a while. Initially you get hot water, but after a while it gets cold again when you let it run. So I think a number of factors hide in the "cp" factor below.

How many of the water/oil molecules get in contact with the walls (engine and cooler) must be a factor. Thus the turbulators in the Mazda oil cooler. Time must also be a factor, at least in terms of letting each molecule move to the wall.

So even if increased speed of flow may not hurt, it seems counter intuitive to make water/oil flow so fast that heat transfer does not take place.

There must be some kind of bell curve where you have a fluid speed for optimum heat transfer. Actually that curve must be a composite of conditions in the engine and of conditions in the cooler. An additional factor for the cooler is how well the heat is transferred from cooler to air. A cold wall should make heat transfer from fluid to air go that faster?

So what kind of instrumentation (measuring points) would enable us to optimize speed of fluid flow?

Finn


On 6/24/2018 4:36 PM, Ed Anderson eanderson@carolina.rr.com wrote:
You said it well, Ernest
 
What you want is heat removal from the engine.  Slowing flow down through a radiator will indeed show a larger Delta T from intake to outlet because the coolant(in the radiator) is exposed to cooling air longer.  That has led many to believe erroneously that slow flow = more heat removal.  I once argued an hour with old man Lou Ross about this issue and when I told him that the obvious conclusion was that if slowed water cooled better, then stopped water would cool best – there was silence on the other end of the phone and then Lou hung up and never spoke to me again.
 
Part of the myth also stems the results when attempts were made to improve flow rate by speeding up the coolant pump expecting better cooling.  When worst cooling occurred, it was concluded erroneously that the faster flow resulted in worst cooling. In most if not all of those instances, the poor cooling resulted from less flow – the faster water pump was actually cavitating and therefore actually pumping less coolant than at slower rotating speeds where cavitation did not occur.  But, it all fed into the myth.
 
 
Heat duty (Q): Heat duty is defined as the product of mass flow
rate specific heat capacity and the temperature difference
between inlet and outlet fluid temperatures
 
Q = m*cp* DT
 
A rule of thumb regarding heat removal and flow rate is:
 
The heat transfer coefficient decreases by ˜10% with a threefold increase in the mass flow rate
 
 
 
So a 10% decrease in transfer resulting from  three times the mass flow shows that increased mass flow (in of itself) will result in increased heat removal even though the heat transfer rate may lessen slightly.
 
At some point you get pressure losses and other factors - not to mention the greatly increased power required to get the large increase in mass flow - makes it impractical to infinitely increase flow rate.  Once you get the flow good enough to cool your engine under whatever the conditions you are operating within, it makes little sense to waste power to get more flow
 
However, we want best heat removal from the engine.  Heat is removed via mass flow of the liquid – no mass flow = no cooling.  So the more mass flow(within reason) - the more heat is removed from the engine and provided we can get rid of a certain amount of that heat though the radiator the more cooling of the engine occurs. So it’s a system, the cooler the oil returned to the engine the better heat transfer, the more mass flow from engine to radiator the more cooling, the cooler the air flowing across the radiator the better the heat rejection, etc.  All factors contribute and you can not focus on just one factor, the optimum cooling results from the optimization of all the major variables involved for a particular situation.
 
Just my 0.02  Back to my cave
 
Ed


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