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Watercooled PC from James Collins
Date 28th September 1999
Author James Collins
Editor James "Agg" Rolfe


James Collins sent in some pics of his great water-cooled rig!

 

P-III 550 OC'd to 645 @ 117 Mhz. I have a teflon based cover over the front of the copper plate of the cpu and foam-based insulation on the processor side to eliminate condensation. The operating temp of the cold side stays at 55-60 F at 75-85 F room temp @ 35-45% humidity.


The copper tubing was purchased from a local hardware store. It is 1/4" soft copper refrigiration, 15' Ft, coiled in a double cone: The spiral starts out at 4 1/2 " winds in to 1 1/2" and back out to 4 1/2". I did that for maximum surface area /air volume exposure. The pump is a standard pond pump, 325 GPH. "Becket" brand. They are extremely durable and produce relatively little heat. The coolant used is 95% Distilled water and 5% ethylene glycol. (NOT ANTIFREEZE!!) In use of smaller coolant loops, in my studies "antifreeze" has too much heat retention for practical use and also inhibits water volume and flow.


My cpu heat exchanger is actually a electronic project box with a aluminum backing. The backing has a pentium class heatsink bonded to it, and is sealed in the box with epoxy, the heatsink transmitts heat to the coolant more efficently then if I just had the aluminum plate. On the CPU I used a copper alloy plate(typically used on heat exchanger gaskets and noncorosive, too) @ 1.2 mm thick. The cache and cpu core contact the plate and are sealed on the processor side by .9 mm thick pliable sheet foam and the front side of the plate is a teflon based plastic called "Sigma"@ .6mm It is produced by my company and has excellent insulation properties.

The return reservoir coolant measured temp in normal operation is appox. 10 - 12 F higher than room temp. The peltier junction is a 24V high density 42 mm^2 unit powered at 12 V DC @ 9.2 Amps. The power supply is actually a standard 400 watt AT, the smaller unit on top (another like it is mounted in the case, which supplys the fans inside the case) is a 18 VDC @ 2 Amp power supply. It powers the cooling unit fans, which at 160 cfm produces 62 db of noise (ouch). The PCB has a temp regulator which monitors the cpu temp, and adjusts the peltiers power supply accordingly. I keep the cpu at around 55-58 F, testing has proved that with my Intel p-3 550 I can run at 645 reliably at CPU temps up to 78 F.


The housing is actually a SCSI external case, which has removable sides and top. I had to tack weld the front of the chassis prior to mounting the fan, because it was cut out for easy punch and removal of drive slots.

Why don't I attempt to go faster? Well, I have seen speeds up to 728 MHz with this design, but the cache becomes an issue, I can cool the CPU and cache down to -19 F, and the cache still will not fucnction properly. My design goals were to make a self-contained, clean and simple unit to provide stable operation of a CPU at 1 to to 2 bins over it's rated speed. My final production unit has been in use since May of this year with no problems.

All original content copyright James Rolfe.
All rights reserved. No reproduction allowed without written permission.
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