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Tracy, I went and
researched the boiling point of gasoline and you hit the nail on the head - the
different components boil at different temperatures making the overall mix very
unpredictable. Also, different manufacturers and grades boil at widely
different temps. As expected, aviation fuel is more consistent and boils
at a higher temperature. I never found a particular number but always a
range of temperatures where components began to boil off. The spread of
those ranges went something like:
70's-150's F for winter
blend mogas, up to
mid 100's-high 300's for
avgas.
The problem with boiling
the fuel is that most of it will then escape out the vent before it can
re-condense. I'm sure this will more than offset any fuel gains from
drag-free cooling. Even moderately raising the temp (and vapor pressure)
will probably cause excessive evaporative loss of the fuel. We have to
face the fact the fuel is not an acceptable coolant for this application.
That's OK, there is still Evans or water and the rest of the wing surface to be
used.
If we can cool our engines
with a few square inches of frontal surface, I know there is enough cooling
capacity in those wings to do most of that work. All we have to do is
build it into the design of the aircraft. (simple as that)
:-)
Dave Leonard (also
dreaming of drag free cooling)
Boiling the fuel? Isn't this the same as trying to re-refine the
gasoline? I think this would cause all sorts of stuff to be distilled out
and clog the fuel line. My $.02
Wendell
To amplify why vapor lock is not an issue here (assuming we
get adequate "tank cooling"), my plan was to cool the oil which gets to
a much higher temp than the coolant. I never got around to
finding out the boiling point of gasoline (anyone here know?) but it was my
HOPE that it would boil which would vastly increase the heat absorbed from
the oil. When the gasoline "steam" returned to the tank, it would
immediately cool and condense to it's liquid state, even if the tank was
almost empty.
Possible flaw is that some components of gasoline might be more
volatile than others, remain in vapor state and escape from the tank
vent.
Tracy (still dreaming of drag free cooling)
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