I think you failed to actually read TFA. Unlike you, I know almost nothing about heat dynamics, nor about FEA, so my comment is predicated entirely on the Sandia staff being truthful in their video (and being quoted accurately in ars's Q&A article). I claim zero authority on the subject.
Your top-level comment claims that the breakthrough in this is in the thin-air gap, rather than in the centrifugal force. Respectfully, Sandia's Jeff Koplow specifically claims otherwise, in detail.
Koplow claims the boundary layer is the key problem (a claim with which you appear to agree). He further claims that when the radiator is spinning (or otherwise accelerating) that the boundary layer thins, and that in their application it thins by roughly 10x. See the video at 1:25 or so. And while I don't trust my under-educated intuition particularly heavily, it's very easy to imagine how accelerating the fins is fundamentally different from blowing air across them, in terms of how it affects air molecules in the boundary layer. Again, note that you specifically claimed "There is no difference between spinning the heatsink and moving air at the same velocity across stationary heatsink fins", and Koplow has specifically claimed that this is not true.
The fluid dynamic bearing only becomes relevant as a secondary problem: if you're going to spin your radiator but not your heat source, obviously there's a transfer problem. Apparently this is easy enough to solve, I guess? Koplow did mention (a year ago) that they were considering adding roughness to the revolving surfaces to perturb the air in the gap to improve transfer.
Oh, and you repeatedly say "they should use fluid". Well, first of all my little pedantic nit-pick is that air is a fluid. But more interestingly, the article contains a link to Q&A with more technical details, in which that very subject is discussed! The short version as I understood it is this: viscosity kills you.
I guess what I'm saying here is this: you started off by saying the article was wrong (about the centrifugal force), and went on to question all the design choices involved, but I think you actually skipped the bit where you read the article in enough detail to know whether or not it was wrong. Even though you obviously have a much better background in the material than I or most other commenters.
This news isn't new. Articles and at least one paper came out, if my memory serves me, two to three years ago. Back then I went through the available data in detail. I didn't need to dive into the article posted to HN to know what they were doing. Still, I did read the entire article and watched the video before posting.
As for the boundary layer issue. A fluid (OK, liquid) based cooler has virtually none of these problems and does not require having MULTIPLE metal masses inside your computer spinning at 5,000 RPM (per the paper on the Sandia site).
Remember that you need to cool memory, graphics cards and other elements in a typical design. The air-based CPU cooler moves air around the CPU cabinet and out the back or top. All of it serves to cool other elements. Dust or not.
You can't put a bunch of 5,000 RPM coolers inside a
In a typical data center you have reasonably-clean air available. Dust should not really be a problem except for the most neglected portions of an installation. I have seen systems in service for years with no indications of dust accumulation at all.
Dust can be an issue in office or home environments. Even then, from personal experience (and only from personal experience) I have never seen a problem.
I do think that the Sandia heatsink might have interesting applications as part of the heat-exchanger in a liquid-cooled system.
If you have a centrifugal fan turning at 5,000 RPM you are going to move a lot of air radially out. So far all of their experiments seem to show the device working well in the context of pretty much an open air environment. You can't have this pump simply circulate hot air inside a computer cabinet. Because of that you will need to surround it with an intake structure as well as an exhaust structure. This device sucks a lot of air at 5,000 RPM. That, without a doubt, will be noisy.
There's also another element here that is not being compared. How many cubic feet per minute of air is this device moving? How would a stationary fin heatsink perform if you moved that much air through its fins.
A few years ago we modeled and built a custom heatsink that consisted of a centrifugal fan mounted at the center of a field of fins located at the exhaust of the fan. Put another way, fan mounted at the center of a flat plate, intake is at the center, exhaust is radially outward. The fins where located to "grab" and channel the exhaust flow. They were also "ducted" meaning that the top of the fins had a "roof" so no air could escape without bathing the entire fin. This heatsink performed very well. Expensive to manufacture, but it did very, very well. We could custom machine boundary layer control elements into the fins and do better yet. The fan was an off-the shelf plastic DC brushless centrifugal fan with no thermal properties other than moving lots of air. And it was quiet.
I am not necessarily putting down the Sandia fan. I am simply saying that one should be careful not to be attracted to new shiny things without a little critical thinking. I have seen companies waste millions by jumping into technologies that sounded great on paper an were later found impossible to commercialize due to a million real-world issues.
Your top-level comment claims that the breakthrough in this is in the thin-air gap, rather than in the centrifugal force. Respectfully, Sandia's Jeff Koplow specifically claims otherwise, in detail.
Koplow claims the boundary layer is the key problem (a claim with which you appear to agree). He further claims that when the radiator is spinning (or otherwise accelerating) that the boundary layer thins, and that in their application it thins by roughly 10x. See the video at 1:25 or so. And while I don't trust my under-educated intuition particularly heavily, it's very easy to imagine how accelerating the fins is fundamentally different from blowing air across them, in terms of how it affects air molecules in the boundary layer. Again, note that you specifically claimed "There is no difference between spinning the heatsink and moving air at the same velocity across stationary heatsink fins", and Koplow has specifically claimed that this is not true.
The fluid dynamic bearing only becomes relevant as a secondary problem: if you're going to spin your radiator but not your heat source, obviously there's a transfer problem. Apparently this is easy enough to solve, I guess? Koplow did mention (a year ago) that they were considering adding roughness to the revolving surfaces to perturb the air in the gap to improve transfer.
Oh, and you repeatedly say "they should use fluid". Well, first of all my little pedantic nit-pick is that air is a fluid. But more interestingly, the article contains a link to Q&A with more technical details, in which that very subject is discussed! The short version as I understood it is this: viscosity kills you.
I guess what I'm saying here is this: you started off by saying the article was wrong (about the centrifugal force), and went on to question all the design choices involved, but I think you actually skipped the bit where you read the article in enough detail to know whether or not it was wrong. Even though you obviously have a much better background in the material than I or most other commenters.