As we continue our quest to "Overclock" the world, one thing always seems to prevent success, HEAT. We have played with every conceivable cooling solution imaginable and simplicity always rules. The most cost effective and easiest solution is water cooling with a peltier (Thermal Electric Cooler) element to reduce temperatures below freezing (0C). There are now many vendors offering aluminum and copper water blocks for these types of solutions, yet in each case the "efficiency" capabilities are limited by the production costs and design. While browsing the Web one day, I ran into the "coolest" exchanger that I had ever seen at Bunny's Workshop. This design and fabrication could easily be verified as the most efficient I have ever seen.
Since Copper has three times the thermal conductivity of Aluminum, Copper is the natural selection for a high efficiency heat exchanger and cold plate.
I spent better than a month attempting to find 3/8" square copper tubing to build one of my own and only came up blank, so it was time to put on the thinking hat. Well I had to resort to available materials that I could get my hands on. Since I had been getting all my materials from Online Metals, I ordered 1/8" x 2" copper bar stock for the cold plate, 3/8" x 2" copper bar stock for the exchanger, 1/2" x .065" copper tubing for the risers and 3/8" copper round bar for "plugs".
The 3/8" x .065 copper tubing was idea for the risers as it was 'thick' enough to be machined and would accept a 1/8" pipe tap for the fittings. The 1/8"cold plate material was cut into 3.75" lenghts, the 3/8" exchanger material was cut into 3.85" lengths and the 1/2" tubing was cut into 2.5" lenghts.
Using a heavy duty drill press and a 6" cross vise, I machined the 1/2" tubing with a 3/8" end mill, cutting a 2" long slot, .325" deep into the tubing. In order to provide coolant passages into the heat exchanger, I decided again to use the drill press. I drilled 5 (five) 9/32" holes, 2" deep into one side, turned it over and drilled them through the block. The idea here was that the exchanger must be able to be constructed with tools available to anyone.
Once I had made all the necessary parts, I had to solder them together. The .065" copper tubing, after the slot was cut in, provided a 'ledge' for the main exchanger body to seat against insuring a good solder joint. I clamped the pieces together and soldered them with pure silver solder and 'tinning' flux purchased at the local hardware store. Propane soldering kits could also be purchased from the same store for about $20.00 bucks. The exchanger and cold plate were drilled for six (6) 6-32x5/8" stainless steel allen head cap screws to attach them together.
I had already purchased four (4) ICE-71 TEC's from Tellurex Corporation that I had used with the Aluminum exchangers, so each unit was assembled. (Sorry I didn't take a PIC of the 1/8" foam gasket that was used around the TEC's and between the plates.)
I purchased nylon 1/8" pipe to 3/8" barb 90º fittings at the local hardware store, wrapped them in teflon tape and installed them in the exchangers. Rather than attach the processors to the cold plate with screws, I elected to bond them to the cpu core with thermal conductive epoxy from Epoxies, Etc. Their 50-3100 epoxy has a thermal conductivity of 2.1 W/m*K, were as the typical silicone grease is about .5 W/m*K up to the best, Arctic Silver, which is about 4.8 W/m*K. Also this allowed me to bond the entire face of the cpu 'flip chip', increasing the contact area by 525%.
I put the computer back together and fired it up. The improvement was immediate. The copper exchangers quickly dropped the PIII Coppermine 800E's to -11C, six degrees colder than with the same voltage on the aluminum exchanger and coldplate.
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