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Michael, yes, but you are writing your answer from a modern car ideal
engineering standpoint, the increased flow argument as we usually talk
about it with British cars isn't about which is better for maintaining
ideal temperature, it is about which is better for lowering engine temps,
at least that is the way most are looking at it I think.
Greg
On Sun, Jul 28, 2019, 10:29 PM Michael Porter <mdporter@dfn.com> wrote:
> On 7/28/2019 9:02 PM, Greg Lemon wrote:
>
> I read the reply and my first response was, "don't you want the water to
> pick up more heat in the engine so it can shed it in the radiator?" Then I
> thought some more, I think the point is higher flow gives you closer to
> equilibrium, rather than hotter water in the engine and cooler in the
> radiator, and since the engine is the hot spot the closer you can get to
> equilibrium on the temp the better??
>
> On the basis of thermodynamics, no. Heat transfer depends upon the
> temperature differential. The higher the delta-t, the greater the heat
> transfer.
>
> This is complicated a bit by engine temperature affecting fuel
> efficiency. The hotter the engine runs, the higher the efficiency of the
> engine because the heat transfer delta-t from combustion gases to the
> engine parts is lower, so more heat energy is available to do work. This
> is why virtually every manufacturer was doing R&D on very high-temperature
> ceramic engines in the `80s and `90s (which invariably was not workable
> because ceramics were extremely sensitive to thermal shocks, and there were
> a lot of practical limitations to ceramics, like making durable threads in
> ceramic parts).
>
> But, if we're talking heat *rejection*, a big delta-t is desirable. At
> the same time, elevating the engine temperature is helpful in terms of
> efficiency (which is why, as manufacturing processes became better,
> aluminum heads became common, gaskets got better, engine operating
> temperatures went up, from ~ 160 deg. F in the `40s, to ~ 180 deg. in the
> `50s-`60s, to ~ 195 deg. today.
>
> So, the optimum would be a system which maintains a high engine operating
> temperature and a cooling system which rejects as much heat as possible, so
> that the inlet coolant to the engine is as low as possible, in order to
> remove as much waste heat as is practicable without depressing engine
> temperature (which is why the thermostat is still in use). All this needs
> to be done at pressures which prevent nucleate boiling, which greatly
> reduces heat transfer.
>
>
> Cheers.
>
> --
>
>
> Michael Porter
> Roswell, NM
>
>
> Never let anyone drive you crazy when you know it's within walking
> distance....
>
>
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<div dir=3D"auto"><div dir=3D"auto"></div>Michael, yes, but you are writing=
your answer from a modern car ideal engineering standpoint, the increased =
flow argument as we usually talk about it with British cars isn't about=
which is better for maintaining ideal temperature, it is about which is be=
tter for lowering engine temps, at least that is the way most are looking a=
t it I think.<div dir=3D"auto"><br></div><div dir=3D"auto">Greg</div><div d=
ir=3D"auto"><br><div class=3D"gmail_quote" dir=3D"auto"><div dir=3D"ltr" cl=
ass=3D"gmail_attr">On Sun, Jul 28, 2019, 10:29 PM Michael Porter <<a hre=
f=3D"mailto:mdporter@dfn.com"; target=3D"_blank" rel=3D"noreferrer">mdporter=
@dfn.com</a>> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D=
"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
=20
=20
=20
<div text=3D"#000000" bgcolor=3D"#FFFFFF">
<div class=3D"m_2758578669474107067m_-6730512637779744281moz-cite-prefi=
x">On 7/28/2019 9:02 PM, Greg Lemon wrote:<br>
</div>
<blockquote type=3D"cite">
=20
<div dir=3D"auto">I read the reply and my first response was, "d=
on't
you want the water to pick up more heat in the engine so it can
shed it in the radiator?" Then I thought some more, I think th=
e
point is higher flow gives you closer to equilibrium, rather
than hotter water in the engine and cooler in the radiator, and
since the engine is the hot spot the closer you can get to
equilibrium on the temp the better??
<div dir=3D"auto"><br>
</div>
</div>
</blockquote>
<p>On the basis of thermodynamics, no.=C2=A0 Heat transfer depends upon
the temperature differential.=C2=A0 The higher the delta-t, the great=
er
the heat transfer.</p>
<p>This is complicated a bit by engine temperature affecting fuel
efficiency.=C2=A0 The hotter the engine runs, the higher the efficien=
cy
of=C2=A0 the engine because the heat transfer delta-t from combustion
gases to the engine parts is lower, so more heat energy is
available to do work.=C2=A0 This is why virtually every manufacturer
was doing R&D on very high-temperature ceramic engines in the
`80s and `90s (which invariably was not workable because ceramics
were extremely sensitive to thermal shocks, and there were a lot
of practical limitations to ceramics, like making durable threads
in ceramic parts).</p>
<p>But, if we're talking heat <i>rejection</i>, a big delta-t is
desirable.=C2=A0 At the same time, elevating the engine temperature i=
s
helpful in terms of efficiency (which is why, as manufacturing
processes became better, aluminum heads became common, gaskets got
better, engine operating temperatures went up, from ~ 160 deg. F
in the `40s, to ~ 180 deg. in the `50s-`60s, to ~ 195 deg. today.</p>
<p>So, the optimum would be a system which maintains a high engine
operating temperature and a cooling system which rejects as much
heat as possible, so that the inlet coolant to the engine is as
low as possible, in order to remove as much waste heat as is
practicable without depressing engine temperature (which is why
the thermostat is still in use).=C2=A0 All this needs to be done at
pressures which prevent nucleate boiling, which greatly reduces
heat transfer.</p>
<p><br>
</p>
<p>Cheers.<br>
</p>
<pre class=3D"m_2758578669474107067m_-6730512637779744281moz-signature"=
cols=3D"72">--=20
Michael Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking dist=
ance....</pre>
</div>
</blockquote></div></div></div>
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