General Fan Performance Guide

Lars Olsen writes: "As a complementary article to his comprehensive General Heat Transfer Guide , Dave Smith has written another great article for Amdmb.com called General Fan Performance Guide. This is an indepth guide to the performance of the fans we have in our PC's. Here's a quote: 'The specific purpose of this guide is to take the science associated with fans and translate it into a meaningful document that will allow the reader to understand how fans work and how they apply to computers. It provides a brief summary of DC power and drives. It finishes with an introduction to the concepts of sound generation and measurement.'"

Comments

Where are the vertical cases?

[jandrese]

One thing that has been bothering me for some time is the amount of energy spent fighting convection in a standard PC case. Just look how often your primary exaust is a power supply fan--where the intake is about 2/3 of the way up in the case. Any air above the intake fan (HOT air) has to be drawn back down into the exaust fan or stagnate. I suspect that in most cases that hot air just stagnates (right up where you CD burner, DVD and possibly even hard drives sit).
Sorry for not including a small ascii art diagram that would have made the entire layout very obvious, but the lameness filter wouldn't even let a very dumbed down version of it through. Instead I'll try to spell it out here: (Ironically this is much lamer than just including a simple ASCII art diagram).

The case has the power supply mounted in the normal location, however it is mounted such that the power cord connecter is on the top and the intake vents point downward. In front of the power supply (lining the top of the case) are the drive bays. The top of the case is an open mesh to allow air to escape easily. CD-ROM trays will open upwards (like the Apple Cube) and the floppies will drop in from the top. Each drive will have at least half an inch of space on either side of it to allow air to flow around it. The case will have three (possibly more or less) fans mounted in the bottom blowing upwards. The bottom of the case will be on raised legs that allow air to be pulled in from underneath the case. The motherboard will be mounted normally (since case manufacturers can't really do anything about it). Ideally though you would find some way to mount the PCI and AGP cards vertically.

The rest of this post is an attempt to explain why I think this will work, and an attempt to avoid the lame lameness filter (why can't people who have good records, with say 35 or 40+ karma, get around the lameness filter?).
Anyway, my primary intent with this case design is it reduce the turbulance in the case and to use the natural tendancy for heat to rise in my favor. The input fans at the bottom of the case should keep the entire case at a slightly positive pressure. One thing you must do with this case is sit it a couple of inches off of the ground espeically if the "ground" here is shag carpeting. The drives should not be as close together as they are in a standard PC case, and they should allow air to flow freely between them. In these days of 10k and 15k RPM drives cooling your HDs is perhaps one of the most often overlooked aspects if case design. The only big problem I have with this case is the PCI slots. PCI slots are generally too close together for my liking and they are almost invariably mounted horizontally, guarenteeing that any hot card will create a hot spot on the card above it. Unfortunatly there is little a case manufacturer can do about this so I'm leaving it as a caveat. Having the power supply mounted vertically will mean that the power cord will attach to the top of your computer. I recommend either a specialy modified power supply or mounting the power supply horizontally (with the intake repositioned to the bottom of the power supply) and lengthing the case somewhat or simply leaving the power cords on the top of the case. A crafty case manufacturer might even create a little box for the ends of the power cords on the top of the case that will conceal them from general view. If you need more 3 1/2 bays, you can run them down the front of the case (in front of the motherboard) vertically. The final caveat with this configuration is that your users must remember to never stick objects on the top of this case (especially things that can spill, like coffee cups). I recommend making the top rounded or triangular or some other shape unsuited for sitting things on (but remember to leave access for things like CD-ROMs and floppy drives!).

A similar construction (albiet with more specialized hardware) to this was already used for that Apple Cube (and look how good the cooling was on that, no fan needed!) but it seems like PC manufacturuers still havn't got it. Look at practially any professional server and you'll see similar concepts in play (I'm definatly not claiming I invented any of this) almost exclusivly. Nothing here is new in the slightest and yet nearly every PC case manufacturer insists on the same general layout and same general poor quality construction. Sometimes it feels like the only thing cases are manufactured for is low cost, and all other considerations are secondary. It is this attitude of cutting every corner possible that leads to the air circulation nightmare we have in almost all modern cases. I also believe that high heat lowers the life of PC components, be it through shrinking and expanding or just plain mild constant overheating. This goes double for devices like hard drives which have actual mechanical components and thin layers of oil to worry about.