X-Junk-Score: 0 [] X-Cloudmark-Score: 0 [] X-Cloudmark-Analysis: v=2.2 cv=HLeBLclv c=1 sm=1 tr=0 a=7n2HAuUc1DbeyJ/G+Wel8w==:117 a=vhm3GwjUlMip0Inz7/w+Eg==:17 a=7mUfYlMuFuIA:10 a=r77TgQKjGQsHNAKrUKIA:9 a=Ia-xEzejAAAA:8 a=ayC55rCoAAAA:8 a=z8_eoGVJAAAA:8 a=WVKaCAgM3ZDoTDtkYGwA:9 a=ZKASOuXMRMV0FmnG:21 a=AB2EQYoc7WOIew4Z:21 a=QEXdDO2ut3YA:10 a=4PR2P7QzAAAA:8 a=471OLrJ9PZgT0Vb9AYsA:9 a=y-Sjp5IxdQhAeZm4:21 a=_2SDW_E_T75TcZwZ:21 a=IlY-9sK9CEU72ucK:21 a=_W_S_7VecoQA:10 a=jRNw1R_Mw0TBPWHUY4gA:9 a=HXjIzolwW10A:10 a=KwgpVZE-ergA:10 a=Urk15JJjZg1Xo0ryW_k8:22 a=B_RyunTPg8udlmYm5Cu2:22 a=4dqwQCo7Po2mVW515mGf:22 From: "Ed Anderson eanderson@carolina.rr.com" Received: from [107.14.166.228] (HELO cdptpa-cmomta01.email.rr.com) by logan.com (CommuniGate Pro SMTP 6.2.5) with ESMTPS id 11312043 for flyrotary@lancaironline.net; Thu, 28 Jun 2018 10:34:26 -0400 Received-SPF: pass receiver=logan.com; client-ip=107.14.166.228; envelope-from=eanderson@carolina.rr.com Received: from EdPC ([71.75.201.150]) by cmsmtp with ESMTPA id YXzZfjR0dvBPMYXzlfZdL3; Thu, 28 Jun 2018 14:34:08 +0000 Message-ID: <5D3D12625FBC4AD8833C981D854B4B0E@EdPC> To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: Oil Date: Thu, 28 Jun 2018 10:33:51 -0400 MIME-Version: 1.0 Content-Type: multipart/related; type="multipart/alternative"; boundary="----=_NextPart_000_0261_01D40ECB.81A12A80" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 16.4.3528.331 X-MimeOLE: Produced By Microsoft MimeOLE V16.4.3528.331 X-CMAE-Envelope: MS4wfNfli3U0O9x8PmNPUt0V+A4CpfdLSXL8OD0+VbSyr+ZIWb5OWEbdXxKcasTt4lSVjYfXunIROLVT/+QqpTTX6/0sGcFi5xF1Fa4HdBxEXe9qHa8LRrsV 0z0Dwe3nTLw2fz4cVG0GB4Dd9RgsHnyoUCg= This is a multi-part message in MIME format. ------=_NextPart_000_0261_01D40ECB.81A12A80 Content-Type: multipart/alternative; boundary="----=_NextPart_001_0262_01D40ECB.81A12A80" ------=_NextPart_001_0262_01D40ECB.81A12A80 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Finn Good to hear from you.l You are right, there are lots of factors involved in each one of the = terms of the heat transfer equation that are not reflected in that basic = equation. However, there is not a whole lot you can do about Cp. One thing = I=E2=80=99ve found out is that pure water is the best (ready avaliable) = mass for coolant flow and of course its Cp =3D 1. So for good or bad = that parameter is pretty much fixed for whatever fluid you want to = chose. Given that - then I look at the other two factors, Mass flow and Delta T. While a large Delta T improves heat transfer, = there is a limit governed by how hot you permit your engine to get vs = how cool you can get your coolant. So while you can improve it by = turbulanting the liquid, inserting internal fins or wire turbulators, = larger radiators, etc, again there is a limit. Mass flow on the other hand is pretty straight forward, the more you = have the more you cool. While it appears that if you increase you mass = flow by three times you reduce the transfer efficient by 10% you still = come out way ahead by increasing mass flow. The down side as I see if = of increasing mass flow is that it takes power away from you drive = train. That drain means to get the same power to your prop, you now = need to burn more fuel, which in turn produces more heat, which requires = removal, which --------- Well, you get the idea. So it more about optimizing what is practical to optimize and accepting = there is no final, magic solution {) Nature is funny that way. Ed From: mailto:flyrotary@lancaironline.net=20 Sent: Tuesday, June 26, 2018 1:52 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Oil 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 =3D = 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 =E2=80=93 = there was silence on the other end of the phone and then Lou hung up and = never spoke to me again.=20 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 =E2=80=93 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 =3D m*cp* DT A rule of thumb regarding heat removal and flow rate is: The heat transfer coefficient decreases by =CB=9C10% with a threefold = increase in the mass flow rate=20 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 =E2=80=93 no mass flow =3D 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=E2=80=99s 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 ------=_NextPart_001_0262_01D40ECB.81A12A80 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Finn
 
Good to hear from you.l
 
You are right, there are lots of factors involved in each one of = the terms=20 of the heat transfer equation that are not reflected in that basic=20 equation.
However, there is not a whole lot you can do about Cp.  One = thing I=E2=80=99ve=20 found out is that pure water is the best (ready avaliable) mass for = coolant flow=20 and of course its Cp =3D 1.   So for good or bad that = parameter is=20 pretty much fixed for whatever fluid you want to chose.  Given that = - then=20 I look at the other two factors,
Mass flow and Delta T.  While a large Delta T improves heat = transfer,=20 there is a limit governed by how hot you permit your engine to get vs = how cool=20 you can get your coolant.  So while you can improve it by = turbulanting the=20 liquid, inserting internal fins or wire turbulators, larger radiators, = etc,=20 again there is a limit.
 
Mass flow on the other hand is pretty straight forward, the more = you have=20 the more you cool.  While it appears that if you increase you mass = flow by=20 three times you reduce the transfer efficient by 10% you still come out = way=20 ahead by increasing mass flow.  The down side as I see if of = increasing=20 mass flow is that it takes power away from you drive train.  That = drain=20 means to get the same power to your prop,  you now need to burn = more fuel,=20 which in turn produces more heat, which requires removal, which = --------- =20 Well, you get the idea.
 
So it more about optimizing what is practical to optimize and = accepting=20 there is no final, magic solution {) =20 Nature is funny that way.
 
Ed
 
Sent: Tuesday, June 26, 2018 1:52 PM
Subject: [FlyRotary] Re: Oil
 
Hi Ed, good to see you on the=20 list.

Unincumbered by engineering education when it comes to = flows,=20 restrictions and heat transfer I'm free to ponder the subject.

I = keep=20 thinking about a garden hose laying in the sun for a while. Initially = you get=20 hot water, but after a while it gets cold again when you let it run. So = I think=20 a number of factors hide in the "cp" factor below.

How many of = the=20 water/oil molecules get in contact with the walls (engine and cooler) = must be a=20 factor. Thus the turbulators in the Mazda oil cooler. Time must also be = a=20 factor, at least in terms of letting each molecule move to the = wall.

So=20 even if increased speed of flow may not hurt, it seems counter intuitive = to make=20 water/oil flow so fast that heat transfer does not take = place.

There must=20 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=20 and of conditions in the cooler. An additional factor for the cooler is = how well=20 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=20 instrumentation (measuring points) would enable us to optimize speed of = fluid=20 flow?

Finn


On 6/24/2018 4:36 PM, Ed Anderson eanderson@carolina.rr.com=20 wrote:
You said it well, Ernest
 
What you want is heat removal from the engine.  Slowing flow = down=20 through a radiator will indeed show a larger Delta T from intake to = outlet=20 because the coolant(in the radiator) is exposed to cooling air = longer. =20 That has led many to believe erroneously that slow flow =3D more heat=20 removal.  I once argued an hour with old man Lou Ross about this = issue=20 and when I told him that the obvious conclusion was that if slowed = water=20 cooled better, then stopped water would cool best =E2=80=93 there was = silence on the=20 other end of the phone and then Lou hung up and never spoke to me = again.=20
 
Part of the myth also stems the results when attempts were made = to=20 improve flow rate by speeding up the coolant pump expecting better=20 cooling.  When worst cooling occurred, it was concluded = erroneously that=20 the faster flow resulted in worst cooling. In most if not all of those = instances, the poor cooling resulted from less flow =E2=80=93 the = faster water pump=20 was actually cavitating and therefore actually pumping less coolant = than at=20 slower rotating speeds where cavitation did not occur.  But, it = all fed=20 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 =3D m*cp* DT
 
A rule of thumb regarding heat removal and flow rate is:
 
The heat = transfer=20 coefficient decreases by =CB=9C10% with a threefold increase in the = mass flow=20 rate
 
reference:  https://www.tandfonline.com/doi/abs/10.13182/NT0= 9-A7406
 
 
So a 10% decrease in transfer resulting from  three times = the mass=20 flow shows that increased mass flow (in of itself) will result in = increased=20 heat removal even though the heat transfer rate may lessen = slightly.
 
At some point you get pressure losses and other factors - not to = mention=20 the greatly increased power required to get the large increase in mass = flow -=20 makes it impractical to infinitely increase flow rate.  Once you = get the=20 flow good enough to cool your engine under whatever the conditions you = are=20 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=20 via mass flow of the liquid =E2=80=93 no mass flow =3D no = cooling.  So the more=20 mass flow(within reason) - the more heat is removed from the engine = and=20 provided we can get rid of a certain amount of that heat though the = radiator=20 the more cooling of the engine occurs. So it=E2=80=99s a system, the = cooler the oil=20 returned to the engine the better heat transfer, the more mass flow = from=20 engine to radiator the more cooling, the cooler the air flowing across = the=20 radiator the better the heat rejection, etc.  All factors = contribute and=20 you can not focus on just one factor, the optimum cooling results from = the=20 optimization of all the major variables involved for a particular=20 situation.
 
Just my 0.02  Back to my cave
 
Ed

 

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