在官方FAQ找到了
Which direction should the fan rotate?

The fan of all ATI or NV Silencer coolers should rotate clockwise.
Since a diagonal fan is used, the air is drawn in in a twister.
This gives you the feeling of blowing air.
Nevertheless the cooler is drawing air out of the case, even it is not a big amount

另外...
清灰塵的方法...是
在尾端用吸塵器吸