Notes on project Gamma - Cooling

It is pretty clear that there are two alternatives for cooling this beast, forced air or water. Let's look at them separately.

Forced air is the "traditional" approach. Each EB104 board gets mounted on a heat spreader, made of copper, to quickly get the heat off the parts. CCI sells a suitable spreader for $24. I looked into just buying pieces of copper from McMaster Carr, but it appears to be much more expensive to do that. Once you have a heat spreader, then you need a heat sink. CCI sells a 6.5" x 12" x 1.6" heat sink (their #99 ) for $22. This sink is 54 square inches per inch of surface area, and has a thermal dissapation factor of .79 . It weighs 3.6 lbs. I spoke with them on the phone, and they claimed that this sink was sufficient with forced air at an unspecified volume/rate to cool an EB104.

I'm concerned that there isn't much in the way of thermal discussion on the CCI website, and the person that I spoke with on the phone didn't seem too technical. Insufficient heat disappation would be a great way to ruin this project...

Aavid is one the leading manufacturers of heat sinks. They make a sink (#61785, extruded profile) that is 10.78" x 3.77" x whatever length you want. Thermal resistance at 18" length is .31 , and its surface area in square inches per inch is 92.1 . However, it weighs 16 lb/ft which might be an issue :-)

The Aavid #62725 sink, also extruded profile, is 9.75" x 2.28" by length, and weighs 7.1 lbs/ft. Budgetary price from Arrow is $107 for an 8' bar - part number 627251F0000. At 18" length its thermal resistance is .29 . You can see its thermal properties here. From the graph in the lower left of the page, it appears that with a 100 CFM fan in a channel 3" high by 10" wide (assuming that we box in just this one sink) we get 2.438 meters/second of airflow, which would drop the sink temperature to less than 25 degrees C above ambient. If you believe that the ambient air is in the range of 40 degrees C, that gives you a 65 degree C heat sink, which is fine.

On to the question of the mechanicals. I think we need a commercial enclosure so that everyone can easily repeat the mechanical design. One option is the Basic Kit 19" rack mount enclosure from Techmar . They quoted me $165 for an 8.5" usable height by 24" depth by 16.75" usable width rack mount all aluminum chassis. It is available with perforated bottom, top, or sides.

Mouser carries BUD aluminum rack mount chassis. The 8.5" high by 22" deep ones are $83 quantity one without top or bottom. The top/bottom is $33 each, so the total equivilant cost (to the Techmar) is $149. That doesn't include handles. Internal chassis shelves of various widths are available too.

Another enclosure option is Protocase . They make "custom" cases - you pick a style (U shape or rack mount seem to make the most sense for us), specify cutout locations and the number and locations of captive connectors, and they make up the enclosure for you. They quoted me prices of around $240 for a suitable (24" x 17" x 8" U shape with 10 cutouts and 10 captive fasteners) enclosure. The big benefit here is that we get the mounting holes for the display, buttons, connectors, etc. cut to our specs - and thus we get a very professional look.