There are two kinds of GPU air coolers.
The first is the blower design:
It sucks air in from the front fan, blows it past the radiators over the silicon, and ejects out the bracket end of the card.
The second is the open design:
Air is sucked in from the front fans, blows through the radiators, and out the sides of the card.
Both depend on air flowing past the metal radiator fins to wick heat away. As long as the card has adequate intake and outtake, it should cool just fine.