Paul,

I think I'm beginning to beat a dead horse here, hopefully this will
be my last post on this topic...

To me, the data below suggests very strongly that the piston engine
for which the data are shown is operating in the nucleate boiling
regime... that is why in the high heat flux regions, there is very
little metal temperature rise with increased coolant temperature.
Nucleate boiling is the dominant heat transfer mode, so the coolant
side metal temperature by definition cannot exceed the boiling point
of the fluid. The boiling point doesn't change by increasing the
bulk temperature. In the lower heat flux regions (regions where the
gas side temperatures are lower) you can see quite clearly the
effect of raising the coolant temperature. It's not a degree for a
degree, but the trend is obvious.

This would lead me to want to try running EG-Water at a higher bulk
temperature in the rotary engine... you reduce the margin for
boiling over, you stress the cooling system connections more, but
the engine SHOULD be OK, and the radiator can be made smaller.

But it should also be clear that by changing to a high boiling point
fluid (like Evans) you WILL shift the temperature at which nucleate
boiling begins to a MUCH higher point... Thus, if you run a high
boiling point fluid at a higher bulk temperature, AND if nucleate
boiling is important for heat transfer in the engine, you WILL raise
the metal temperatures, perhaps by a very large amount. Will it
work? I haven't got any idea... it is worth testing... but it is
also worth recognizing the risks. And I do not think the rotary
combustion chamber is inherently more tolerant of high
temperatures... just the opposite. Many of the things you have been
looking at should help... stretchy through bolts, better o rings,
better lubricants... I am very hesitant to jump to conclusions
without adequate testing to support the validity of the hypothesis.

Jon

Sorry folks about not having this nuc boiling chart up sooner. Some of
these concepts can be rather obscure.

Paul Lamar

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