No disagreement with you; I've raced sailboats for years. The point I was
trying to make was that an obstruction in front of an opening will have a
larger effect on the airflow than a smaller obstruction behind it,
especially if the downstream obstruction isn't shrouded. I look forward
to the posting when the car is operating at the ideal temp, so we can
find out what worked best.
Bob
On Sun, 20 Jul 1997 02:23:19 -0400 Trevor Boicey <tboicey@brit.ca>
writes:
>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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