> of clearances and fuel mixture and timing. I don't
> know what
> happens, exactly, when boiling sets in, but it seems
> like an
> explosion.
I missed all of this thread (been busy), but in a
nutshell, boiling point varies with vapor pressure
(search "steam tables" in yahoo or google to get the
numbers). Steam (or water vapor) doesn't transfer
heat as well as liquid water so although water and
steam (if not superheated) are at the same temp for a
given pressure, heat transfer sucks with steam and the
overheating runs away (not to mention the fact that
your water pump doesn't appreciate trying to pump a
gas). With the fan argument, a "puller" is generally
more effective at cooling a heat exchanger (radiator)
because the flow thru the HX is more laminar (the fan
blades "turbulate" the flow), and the pressure drop
will be much lower (if it's turbulent, meaning
Reynold's # higher than 3000 or so, the pressure drop
goes as the square of the flow thru, versus a linear
relationship for laminar flow). You'l also use more
of the hx face, because with a fan in front the
pressure will be at the blade tips, and very little
flow goes throught the center axis of the fan. I can
not overemphasize the importance of a good shroud
around the fan in either configuration.
Search the archives for more detailed examples and
explanations from when I had more time to write...
Ron Soave
When opportunity knocks, don't bitch about the noise.
__________________________________
Celebrate Yahoo!'s 10th Birthday!
Yahoo! Netrospective: 100 Moments of the Web
http://birthday.yahoo.com/netrospective/
|