So here we have a tripple fan unit for the PS3.
It fits nicely to the unit. And so my thoughts. Well its not very powerful, but then the fans are only 5v from the USB. It must be noted that the CFM rating isn't listed for this device. Adn I'm not suprised. It would give you a more cosmetic appearance that you are trying. Anyway for those that don't know CFM stand for cubic feet a minute. ie the air flow. So the higher the airflow the better. On my PC I use a justcool twin tubro fan unit which keeps the PC very very cool and has a rating of 80CFM. I would guess this unit is about 8!
The top vent the fans are trying to suck from has very little air space, hene that won't help either when they arn't that powerful.
But it does reassure you that you've done something completely useless and you can reassuringly hear those fans buzzing away. In fact by covering the top vent up with the fans, you could have made the whole vent situation worse!