I don't have Heisler's "Advanced Engine Technology".  I think I

mis-understood how he

was using the term "nucleate boiling".  I believed this term to describe

the heat

transfer mechanism whereby small amounts of coolant at the metal surface

flash into

vapor, then depart the surface and quickly re-condense in the coolant.

Given that they

quickly re-condense, how can they migrate to the high point of the engine

and form a

steam pocket?  Re-reading Heisler, I see that he uses "nucleate boiling"

all the way to

film boiling.  I guess his definition is correct: nucleation sites are

still involved

the whole way to film boiling.

But there are two distinct sub-phases to nucleate boiling, divided

vaguely where the

vapor re-condenses rapidly after departing the surface (before), and

where the vapor

remains a bubble long after departing the surface (after).  We want the

former since

enormous amounts of heat energy are transferred (i.e. high cooling system

efficiency);

we want to stay away from the latter, as it allows steam pockets to form,

which are just

as bad as stable films (very bad) because they allow localized hot spots

to occur.

BTW, have you seen this paper about adding soap to coolant?
http://www-heat.uta.edu/publications/1995c3.html

Russell Kent

That is probably what Water Wetter is :-)

Paul Lamar

 The way I understood nucleate boiling was that the vapor bubble condensed
rapidly in the coolant, and said so in my post.  This whole discussion has
clarified this continuum of behavior for me, and I hope for others.

Bill Freeman

 
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