Hi ! Something about fans.
If you block the low-pressure-side of a fan (with cables, finger-quards,...) the pressure-increase over the fan is much lower compared to the situation, if you have the barriers on the high-pressure-side (the side, where the air comes out). I remember a lecture, where somebody from papst-fans said something about 25% of the pressure-increase with a flat plate 10 mm near the fan on the sucking side compared to the plate on the blowing side. And then it is possible that you have not enough flow rate. Thats the main reason, why CPU-Coolers blow toward the heat-sink and not the other way. Try to have much room on the sucking side of the fan. If you want to blow cold air from outside, put the fan outside the case and blow through the holes into the case. The air on the sucking side of a fan comes from everywhere, also from the blowing side. This is like your loudspeaker. You can put a small plate in radial direction (the plane, in which the axial fan rotates) to prevent this air bypass. The air on the blowing side goes into one direction and diffuses the farer you are. So you can control the air-stream. I use litte fans in the case to bring more air to critical regions. If you blow the air into the case, the pressure in the case is higher than outside and the (warm) air goes out through every hole, also through your floppy-drive. If you have a dusty room like me, then this can come to a problem. If you blow the air out of the case, the pressure in the case is lower than outside and the fresh air comes everywhere in (This is the situation, if you have only the fan to the outside in the powersupply). If you suck the air out in the front area of your case, you have always warm feet. Do this, if you like this. Warm air goes up, so better try to get the air out of your case in top regions and blow in at the bottom. If you blow the air into the case near the (dusty?) floor you can get a problem with dust. I hope you could get some useable infos out of this. If you have not enough holes in your case, simple make them. But you will lower the protection against electromagnetic waves. The holes have to be smaller than the wavelength if I remeber correct. If your highest frequency in your box is 2 GHz you have to stay under 15 cm. Or am I wrong? How high is the higest freq? How for example is the 2 GHz for the CPU generated? Try to feel like the wind in your case and you will see the problems *grin* Joe On Friday 26 September 2003 14:26, mathieu perrenoud wrote: > After my yesterday's thread, I decided to buy one fan. When I saw the > price, I buyed two instead. But now, I don't know how to place them in the > case. The boxes of the fans says that I should place them at the rear of > the case and make sure they pull air from the inside toward the outside. > Yesterday, you told me that it could be better to pull air inside and the > guy at the shop told me that on his own box he had a fan in front pulling > air inside and one at the rear blowing air outside. > I'm at a complete loss here. Should I follow box's instructions? or the > guy's advice. > I think I'll first try with one in the front and one in the back. If it's > stupid or even dangerous, any quick warning would be greatly appreciated. -- [EMAIL PROTECTED] mailing list
