The New York times wrote this about Mr. Lemont's original Patent No. 5,292,088 for the Propulsive Thrust Ring System in 1994;

"As a motor turns an ordinary fan, a difference in air pressure is created between the front and back of the blades. This lets the blades thrust air outward but also creates tiny vortices -- spinning pockets of energy that are somewhat like tiny invisible tornadoes -- on the surface of the blades. These vortices use energy without producing air flow. To recapture the otherwise wasted vortex energy, Mr. Lemont has added three rings that surround but do not touch the fan's blades and are superimposed upon each other with a small space between them. The rings are shaped like airfoils, preventing the highest-energy vortices from forming at the tips of the blades. The rings let the fan harness the otherwise wasted energy and, by drawing in additional air from its periphery, increase air flow by 200 percent, Mr. Lemont said."

A few years later a short-lived company called Millenium Thermal Solutions was created to adapt the thrust ring concept down to scale suitable for CPU cooling. Patent No. 5,896,917 Active Heatsink Structure with Flow Augmenting Rings and Method for Removing Heat set down the groundwork for the prototype Glaciator heatsink that was to follow. The concept was supposed to reduce noise levels, particularly when compared to the standard brushless DC fans of the time.

The original aerospace concept was distilled from a fan inset into the heatsink body to a series of thin horizontal vents in the frame surrounding the fan blades. The vents augment the way air is drawn into the impeller, and to some degree this reduces noise levels.

The first processor specific iteration of the technology came in the form of the aforementioned Glaciator heatsink. Its fan hub was recessed into the body of the heatsink with the slits formed by copper plates on all sides. Later iterations abandoned this approach for a free standing fan with horizontal slits in the fan frame, allowing the fan to be mounted onto any heatsink, rather than specially designed and built CPU coolers.

You can see an example of the first generation heatsink/fan integration here, the second generation horizontally slitted fan frame used on the Thermaltake Silent Boost heatsink and Coolermaster Hyper TX2, and the final and greatly simplified side-vented fan frame here. What's interesting about all of this is how the genesis of an idea initially developed to solve an issue in aerospace applications has made its way from helicopter engine design to the world of computer cooling, then over several years distilled by commercial PC fan manufacturers to its most basic form.

The Coolermaster Hyper N520 heatsink uses the same style of side-vented fan as the old Coolermaster Hyper 48, only in this case a translucent clear plastic has been selected for visual appeal. The flow augmentation rings of Adrew Lemont's original patent have been scaled down to horizontal openings which probably suit the lower air velocities that a 92mm diameter fan actually creates... or perhaps it's just different enough to circumvent patent claims - there's no way to really know.

Offset 92mm Fans

The other unique aspect of the Hyper N520 are that its two 92mm fans are set off-axis with one another. One fan forces air into the tower of aluminum fins, while the second is positioned 20mm off to the right, drawing air out from the aluminum fins. There are a couple reasons Coolermaster could have chosen this approach, so let's speculate.

A) It mitigates the dead space behind the fan motor where airflow typically stalls and creates a hot spot by inducing angled laminar airflow.
B) The large vertical intake and exhaust ports help alleviate back-pressure issues and to some extent create areas where air is naturally drawn into the cooling fins (think of it like a big Venturi tube that happens to pass by a cluster of heatpipes).

Does all this engineering mean the Coolermaster Hyper N520 heatsink will outperform competing heatsinks on thermal and acoustic fronts? No, not necessarily.... the only way to really discover how a heatsink performs is to test it - so we'll hold off on final conclusions until that data is in.

Heatsink Installation

Coolermaster's Hyper N520 heatsink is compatible with Intel socket 775/771/1366 and AMD socket 754/939/940/AM2/AM2+ processors. The heatsink comes with a set of rear-motherboard support brackets, and a couple metal clips that screw onto the copper base of the heatsink to accommodate the various CPU sockets.

We continue to not be particularly fond of the way the Coolermaster mounting system works; it requires the motherboard be removed from the chassis each time you install or remove the heatsink to access the double-threaded screws and nuts. If you have a computer case which allows easy access to the rear of the motherboard (ie. via a hole cut in the motherboard tray), the system isn't too cumbersome to install.