Designed by researcher Jeffrey Koplow, the Sandia Cooler does away with a separate fan component, and instead relies on the heat sink itself to disperse heated air.
Traditional CPU heat sink designs usually feature a metal heat sink and a fan working in concert to siphon off the heat generated by computer parts. However, that design creates a 'boundary layer' of air, retaining the heat that the fan is supposed to disperse. The power necessary to drive the fan, as well as the fan's proximity to the boundary layer, makes that design inefficient. The Sandia Cooler eliminates the fan, replacing it with a finned heat sink that can disperse the boundary layer far more efficiently since the two are in closer contact.
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I quote: "According to the paper supporting Koplow's findings (PDF), the Sandia cooler could finally offer the cooling efficiency necessary to allow for processor clock speeds above the current rough 3.0GHz limit. "
It's basically spinning heat sink which will generate some noise and spinning element fits into fan description altho it is more. This cooler can be called fanless but sadly it's not at all passive.