single-side fans airpressure is not constant within radiator. the fans must work more to push the rated CFM due to constriction of radiator fins. This slows the air...and we all know slower air yields less cooling.(assuming fans are sucking air through rad).

Add in the second set of fans, the fan blowing air in is not restricted as much at inlet, but is slightly restricted at outlet by radiator fins.

If the fans is blowing into rad, the fan must work against teh restriction of the rad to continue to push the air through the rad. The air slows as soon as it hits the rad, and by the time it exits, it's moving far slower than when it entered.

so, either way, air slowed down through rad.

It LOST energy to slow. It lost energy by friction...which creates a bit of heat. Although this AMT of heat given off is very small, it is detrimental to the air absorbing heat from the rad.


Add two sets of fans...the air should enter and exit at the same speed. you don't get twice the airflow from adding a second set of fans, but those fans will WORK LESS as the load from moving the air is spread out between them.


In the end, the air then needs to absorb energy to maintain the same speed...and lost some due to friction...where does that energy come from?

The heat from the water?