Hi, I have a Corsair 350d obsidian (http://www.corsair.com/en/pc-cases/obsidian-series-pc-c...) and I just have a question about the case fans. As you can see, there are 140mm fan(intake) and 120mm fan(exhaust) but recently, I got two 120mm fans from my friend. He told me to put them on top as exhaust fans but I was wondering if it's gonna help with cooling? I know there has to be balance between intake and exhaust to make a good airflow so I need your advises..what should I do? Please help! Thanks
The arguments can be made for and against mounting those as exhaust fans. Mounted as exhaust they will pull lots of air out of the case, along with the rear fan, and may create negative pressure airflow cooling: ie. more air moving out of the case then into it. The front fan will pump in lots of air under this scenario and the open/vented expansion slot covers and any other hole in the case will have airflow into the case (if you actually obtain negative pressure, less air pressure in the case then outside). [The bottom vent will have your psu fan directly over it and that air flow will be into the PSU].
Mounting them as intake fans will tend to create a positive pressure system. There will always be more air pressure inside then out. This is, for many, the preferred cooling setup. It provides lots of cooler air, it helps keep dirt and dust out of the case (no, not entirely, but better then negative pressure)..
Don't know if any of that helps, but I am running 2 200mm and 1 120mm intake fans (front, side, back) and one top 200mm exhaust. My case has a grill type front and side and cannot be made positive pressure so this cooling arrangement works well.
With yours, I might try reversing the back fan (makeit intake) and then stick the other two up top as exhaust