Pushing air down into the device, well, where is the heated air going? Back upward. It just seems the heated air would be fighting the air being pushed down into the unit.
You may be right, or either way is just as effective. We can agree, cooling fans make a difference where radiational cooling isn't enough.
Oh you wouldn't place a fan pushing cool air in at the top. You're right, that would seriously mess with the thermal flows in the system. A fan blowing cooler air in would be placed lower in the cabinet. I didn't mean to imply one should just reverse the fan direction on top, although I can see where it might read that way.
My guess is that, given the sheer amount of top mount fans available for HT racks, that pulling hot air out works just fine for that particular application. I was just sharing some practical application knowledge. To get the best exchange of air in a space, you move more pushing air in vs. pulling it out. Burn dinner? Set the fan up to blow clean air into the space instead of setting it in the open doorway or window blowing outward.
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