My Experiments with Case Modding

Air Ducting - A Failed Experiment

I had read about homemade air ducting as well as seen ducting used in retail computer systems, and thought I'd try it myself. The theory is that without ducting, hot air that is a byproduct of CPU cooling is re-circulated inside the case. If said air could be directed outside the case, then the air required to cool the CPU would be drawn from vents and intake fans, and not from re-circulated hot air. Therefore, the duct would have the requirement of fitting tightly onto both the CPU fan and the output, with no hot air escaping back into the case. In my case, the output would be the rear case fan outlet with no fan attached, because for one, I did not have another fan with the exact specifications of my CPU fan, and for two, because stacking fans doesn't necessarily create more airflow. The material I used for the ducting was aluminum foil.

In order to fit aluminum foil onto the fan outlet, I needed something there for the foil to hold onto, since the outlet is a flat piece of metal with holes in it. My solution: removing the mechanical parts of an old power supply fan. In this case, any 80mm fan can be used, but since the fan will be taken apart, a cheap fan might be more appropriate. Once I had this piece, I proceeded to wrap aluminum foil around the "fan bracket" to form a duct, and then I screwed the bracket onto the outlet just as I would a case fan. Because the CPU fan is at a right angle to this outlet, I also had to partially cut out one side of the duct, so that when I curved the duct to fit onto the CPU fan, there would not be too much foil sticking out and touching the motherboard and possibly causing a short circuit. Finally, I curved the duct towards the CPU fan and crimped the foil around the edges to make it airtight. I had finished my new CPU air expulsion duct.

The results: increased CPU temperature and increased case temperature. Placing my hand at the duct outlet, I could feel that the air was hotter than anything I had ever felt coming out of a computer air vent. This meant that the duct was working as it should, as it was moving used CPU cooling air to the outside. So why the temperature increases? I have a few theories. First, computer cooling is not simply a matter of temperatures. Forced air cooling is dependent on the constant movement of air, and the duct reduced the amount of air moving through the case. Second, the duct concentrated warm air inside itself, air that normally would be distributed throughout the entire case (remember, air is always moving inside a case). Third, the duct was comprised of aluminum, a relatively efficient material for transferring heat (most heat sinks are made with aluminum). Because of the concentrated hot air, and because of the duct material being aluminum, the duct acted like a heater inside of the case, causing both CPU and case temperature to rise higher. That is my unproven theory, and although the duct failed to lower temperatures, I did learn a bit about computer cooling.