Monday, October 07, 2002

Convection cooling

Convection coolers, also known as "Heat Pipes", are relatively new to the public consciousness.

Heatpipes are vacuumed tubes with a bit of fluid inside. Heatpipes work on the principle of phase change and are a very efficient means to transport heat to a different location, where you then of course still need to get rid of it, in a heatsink/fan outlet. The main disadvantage of heatpipes is that they are quite stiff tubes, and somewhat expensive, moreover they only solve the problem of getting rid of the heat around the processor and MB.

While heat pipes are more effective than forced air cooling, they are also bulkier, and more costly.

Peltier coolers

A second class of cooling devices can also be placed within the convection category: Peltiers.

Peltier cooling devices do not use fluid convection to circulate heat away from the CPU, but rather use a special assembly of heat reactive material to transport heat from one surface to the other by means of an electrical current flowing through them. Unfortunately they are in their current form very ineffective, but does provide a means of obtaining an actual temperature difference enabling (in theory) a lower temperature on the processor than the ambient temperature.

This however only work when you are able to remove both the heat from the CPU and the Peltiers at the same time. At the current power consumption and effectiveness of Peltiers that means removing over 300 Watts in order to get the temperature in the neighborhood of 0 degrees.

Phase Change coolers

Freon is a gas that has been used for refrigeration more than a decade ago. It has now been replaced by R134 which is a lot less environment detrimental than Freon. Coolers that use R134 operate on the same principals as air-conditioners, and domestic refrigerators.

Coolers using these such gas are also named Phase Change coolers since the phase of the gas used changes from liquid to vapor and back again at precisely predetermined temperatures depending on the pressure. It will vaporize at -45 to -50 at certain vacuum, and condense back into liquid form at a specific higher pressure at little over room temperature. That's why these systems utilize a compressor and a capillary tube, in order to obtain these pressure differences in the system.

Historically, R134 cooling had to be adapted for use with CPUs. Instead of passing cold air directly over the processor itself, a metallic head where one side of which is in contact with the CPU and the other to the compressed R134 -- is used.

By doing so, the total amount of condensation that occurs is reduced, thus avoiding the stress on sensitive electronic components.

Few manufacturers are actually selling Phase change coolers at present, due to the cost and complexity of the technologies involved. It is also true that, while its easy to use Phase change coolers to transfer heat away from the CPU, it's much harder to avoid the condensation that's generated as a result of their operation.

The main manufacturers of R134-cooled systems are Kryotech, Asetech a Danish company that are the builder of Vapochill, and Chip-con (another Danish company)-- who are the maker of the new Prometeia system that we'll be reviewing in this article.

Next: Prometeia vs Vapochill.

Prometeia