blowers vs fans

[Red Squirrel]

Something I've been wondering, why is it that some applications use blowers instead of fans? By comparing various fans/blowers it seems for the same physical size you get about the same CFM, but blowers require more power. Blowers are designed better then fans so I assume this is why. Also, what exactly does static pressure mean? Static pressure is simply how "hard" it is to push the air right? For example if you have a computer case with only fans blowing in, the static pressure is higher since the fans are working against each other, is this what it means? I would assume because of the way a blower is made, it would be able to have a better power against static pressure, but I'm not really sure. I'd like to get more explaination. I'm a lot into this physics stuff so throw me some facts/corrections

 

[CTho9305]

Static pressure means the pressure differnece it can create with no airflow. Take a tube of water, and put a fan on the top. The fan will lift the water a certain height. The most useful measurement is a curve of CFM vs pressure. Blowers are good because in an environment where a lot of pressure is required, they still put out a lot of CFM. Note that heatsinks resist airflow, so while a normal fan starts reducing the amount of air it moves because of the pressure, a blower will stay closer to it's "normal" output.