I think that is the mechanism on the micro level.
This data is on the macro level. This happens to be from
Heinz Heisler
book but confirmed by many other references.

Paul, On the micro level this would have to be true in any solid to

water heat

transfer where the heated object transfering to the water has parts

above boiling

temperature. We REALLY need to avoid that MACRO boiling thing! Bill

J

"Kevin R. Walsh" wrote:

The two forms of boiling are nucleate and film boiling.

In nucleate boiling small nucleation sites vaporize the coolant and a
bubble forms.  You still have fluid to solid contact in most places,
and you can still transfer a significant amount of heat from the solid
to the fluid.

In film boiling the entire surface of the solid becomes so hot that the
fluid is no longer in contact with the solid and a film of gas
seperates the two.  This gas can transmit significantly less heat and
as such your cooling capacity is diminished.

Back when I was an in school we did an experiment with a heating coil
and liquid nitrogen.  We could measure the amount of power put in and
the temperature of the coil.  The rate that you could remove heat was
about 1/4 when you entered film boiling vs the nucleate boiling regime.

Let's just say that if you went into film boiling in your rotary things
would get very bad very fast.

Kevin

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