[TR] water pump
grglmn at gmail.com
Mon Jul 29 08:31:24 MDT 2019
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.
On Sun, Jul 28, 2019, 10:29 PM Michael Porter <mdporter at 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
> 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.
> Michael Porter
> Roswell, NM
> Never let anyone drive you crazy when you know it's within walking distance....
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