ROBERT G. HOWARD wrote:
>
> My assumption is that the airflow was originally channeled through the
> radiator because the radiator support bulkhead had only one opening, for
> the radiator, and the air went on through it. Having passed through, it
> could be pulled through the fan or could flow around the fan, depending
> on road and air speed. Now that there is a fan in front of the radiator,
> the airflow is restricted at 70mph unless the fan is on.
Obviously there are many factors here, so it is likely that
having fans before and after will be different.
But of note, your post seems to be of the opinion that a fan
behind the radiator won't "block any air because it will just
flow around it".
Well, that's not really true. If the fan is obstructing behind
the rad, it can stop air flowing through and leave the rad in
a cluster of still(er) air. Much like a parachute makes a packet
of still air below it that makes the whole chute and rider
very resistant to flow. (the vacuum created above the chute helps
as well).
To back-annotate to your own analogy of rocks in the pond, you
can block water flow over a point by putting a rock in front
of it, sure. But you can also reduce flow rate by putting a
rock behind it, which creates an area of reduced flow in front
of the rock over the point.
This is especially true of rads, which channel air straight
through their fins. Once air is into the matrix, it can't flow
"around" anything that blocks the exit. It could just stop,
then heat up to where it doesn't help cool much at all.
--
Trevor Boicey
Ottawa, Canada
tboicey@brit.ca
http://www.brit.ca/~tboicey/
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