Yeah i don't see it working much if at all unless it's a sealed connection like Reaver showed.
if you have 2 of the same size fans it'd help a little but only cuz the first one is already moving air so the second one doesn't have to do as much work.
Basically, unless the second (outside) fan is larger then it's not gonna show much if any improvement at all because it won't be able to move the air faster because the first fan is already moving the air through almost as fast at the 2nd can.
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