There’s a fundamental flaw with fan-and-heatsink cooling systems: no matter how hard the fan blows, a boundary layer of motionless, highly-insulating air remains on the heatsink. You can increase the size of the heatsink and you can blow more air, but ultimately the boundary layer prevents the system from being efficient; it’s simply a physical limitation of fan-and-heatsink cooling systems in specific, and every kind of air-cooled heat exchanger in general, including air conditioning and refrigeration units.
But what if you did away with the fan? What if the heatsink itself rotated? Well, believe it or not, rotating the heat exchanger obliterates the boundary layer, removes the need for a fan, and it’s so efficient that it can operate at low and very quiet speeds.