These exhaust fans (yes, it is an exhaust fan) make no sense. You want cold air to enter your case from the bottom and warm air to leave your case from the top.
This is important in order to move the air as it does by nature (warm air rises).
An exhaust fan that is installed at the bottom (like this) is not going to be efficient. Sure, it moves air. But, you can achieve better results (cooler or quieter, or both) if your exhaust fans are up and intake fans are at the bottom.