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Review: Asetek VapoChill XE

by Ryszard Sommefeldt on 23 August 2003, 00:00 4.5

Tags: Asetek

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Introduction



Phase change cooling isn't new. It's been the mainstay of almost all commercial refrigerant systems for almost 100 years, and the chemistry behind it dates back to Nicolos Carnot in 1824, who realised that you could keep something cold by transferring the heat away from it to another hot body.

It's that concept that underpins almost all cooling systems in use today, worldwide. You take a refrigerant material, in the past usually a group of chemical compounds known as Freons, which itself is a collective name for a type of chloroflourocarbon (CFC), and you compress it in the first stage of the refrigerant cycle, to a liquid. You then pump it round to an evaporator, the site at which you want to remove heat (and therefore cool). At the evaporator site, your liquid refrigerant expands to a gas. Physics dictates that expansion to a gas means increasing the volume, which conversely means a drop in pressure. A drop in pressure means a drop in temperature, the key to your cooling system. The gas is then recompressed to a liquid (increasing temperature due to an increase in pressure) and the heat produced by compression is removed from your system by a heat exchanger, usually a type of radiator.

It's worth pointing out that Freon's (CFC's), as a compound for refrigerant systems, aren't used in commercial cooling units any longer, due to damaging effects on the environment. Commercial units, such as Asetek's solution for the VapoChill, use coolants like R134a (tetraflouroethane) which are safe and environmentally friendly.

Got that? It's pretty easy when you think about it, just a simple evaporation/compression loop involving a compatible refrigerant with heat exchange at two points, at the evaporator (to cool) and at the compressor (to remove the heat 'collected' by the gas). Even I can grasp that!

It's simple thermodynamics (specifically gas-phase kinetics, if I've read my old physics texts properly), and shouldn't be hard to follow.

Now all that applied to the real world means cold food and drink, keeping your fruit and vegetables from rotting and your milk from going sour. But that's a boring application for refrigeration, who cares about human sustenance and basic survival? What we care about at HEXUS is cooling things so they run faster. We do it with heatsinks, we do it with water cooling, and nowadays we also do it with phase change refrigerants.

Obviously, the benefits of a phase change refrigerant system are easily apparent. Given the right refrigerant material (again, usually a Freon), and a suitable compressor and evaporator loop, things can get very cold. Copper to air only works so well as a heat transfer medium, and with air being the heat transport out of the system, you can never cool below ambient air temperature. Not good enough I hear you cry!

Well Asetek (and others) also heard that cry. They watched the enthusiast sector bumble along with ever sophisticated water cooling systems, and the more adventurous among that community started to experiment with things like submerged silicon oil cooling and phase change powered water and liquid chillers. Being the forward thinking chaps that they are, they soon realised the community was going to have a demand for high performance phase change cooling. And since the base technology has been around since the early 1800's, and in the past century perfected into household, low cost, high performance refrigerant systems, there was a huge market of commercial parts for them to take advantage of.

So Asetek bundled a custom made evaporator loop with an off the shelf commercial compressor, filled it with a compatible refrigerant, supplied the whole lot in a PC case with kit to attach to a CPU, a control unit, and called it the VapoChill. It's a bit more complicated than that, especially when talking about the evaporator/compressor loop (there's throttle and condense stages too), but it's enough for us to be getting on with, to understand how VapoChill works. Kryotech will claim first to market with commercial phase change processor cooling, but Asetek (and recently Chip-Con) were the first to mass market and widespread enthusiast appeal. Indeed, Kryotech should have this market sown up, with the first commercially available 1GHz x86 setup (chilled Athlon 700MHz if memory serves), but high price kept them out of things.

In stepped Asetek with their first VapoChill systems, with barebones appeal (Kyrotech seemed insistent on selling full systems) so you could knock up your own PC around one. They've been market leaders ever since. It's not a massive market, only Asetek and Chip-Con seem to want to play, but it's a market nonetheless.

With a crappy physics lesson out of the way, and some basic market history in your noodle, let's talk about VapoChill specifics some more.