The air is being pulled OUT of the heat sink, and it seems it would be more effective if it was sucking air in (the northbridge gets hot as *#@!, and if the fan was reversed, it would help to cool it, and the PSU fan is right above it pulling air in, meaning they are fighting each other).
Not sure on the electronics part of things.
More about :reverse fan direction stock intel cooler
The heat sink draws the heat up (or rather sideways) and away from the chip, and the fan aids with this process and draws the air away from the heat sink fins. It's more efficient than blowing warm case fan air onto the chip and heat sink.
I have no idea if you can reverse the fan, however the blades are tailored to move air most effectively in only one direction. It would be better if the fan can be unscrewed, and turned over, so you reverse the airflow, not reverse the way the fan spins.
The other little thing I would take into consideration is that a lot of research has gone into making a heatsink/fan cool properly. If it worked better the way you are talking about, I am pretty sure it would already be like that.
But, no harm in trying and see what happens as long as you keep your eye on the temps.
k, all the Intel CPU coolers I've seen blow air down onto and through the heat sink fins, since the point is to transfer the heat from the heat sink fins to the air. If yours does the opposite, it may be defective.
Well, faced with the same issue of the PSU being right over the CPU in a ITX set up.... I did the following...
Promptly voided my warranty on the PSU and flipped the PSU fan upside down causing it to suck air in from out back of the case and BLOW the air into the fan of the CPU. Placed a second small fan in the case as an exhaust fan. Biola! Cool air for all that need it. Hope this is helpful..... and yes, I know that it may make the CPU dusty..er soon..er....but, it does work.