I thinking about building something like the Senfu Tech Station, but I have some worries about airflow.
How can I prevent the heatsink fan from sucking the hot air that is comming from the heatsink, so it will not recycle the air over and over??
im thinking that since its an open case it wont recylce the hot air it will be getting cold air...i think your thinking about a closed case with no intake or exhaust fans, that causes hot air to be recylced
I use a Senfu tech station as a test rig and have no problems recirculating the heatsink air. A typical setup on the tech station runs 6-10°C cooler then when I put it in a case. Most of the heatsinks that I run on it are of the "blow down" variety, but some are also the "suck off" kind and both types work fine.
If you're really worried about it, you could mount the board on the bottom shelf and strap a fan to the frame, run it at 5V and keep a little fresh air blowing around the HSF area of the board. Here's a pic of my tech station. Note the 5V Panaflo that I have blowing on the HDD, this could be blowing on the mobo instead: