NF-A14x25 G2 Technical Background

NF-A14x25(r) G2 performance: improvements for heatsinks, radiators and cases

Noctua’s NF-A14 is renowned as being among the best 140mm fans on the market and has received more than 100 awards and recommendations from the international press. With its further improved efficiency and novel, state-of-the-art engineering, the NF-A14x25 G2 represents another step up in performance.

As can be seen from the following P/Q chart, the NF-A14x25 outperforms its predecessor in the entire spectrum from low-impedance, airflow demanding applications all the way to high-impedance, pressure demanding configurations:

In real world testing, the performance gains of the NF-A14x25 G2 over its predecessor are particularly significant on water cooling radiators. With both fans adjusted to the same on-application noise level on a 140x36mm radiator and a 200W heatload, the NF-A14x25 beats its award-winning predecessor by almost 3°C:

This significant performance advantage of the new NF-A14x25 G2 can also be converted into an acoustic advantage by reducing its RPM speed: Adjusted to provide the same cooling performance as the first generation NF-A14, the new G2 model can run several dB(A) quieter in typical radiator configurations. For example, on the 140x36mm radiator used for testing, the NF-A14x25 G2 could be run at only ~1200rpm matching the performance of the NF-A14 at ~1500rpm, which results in a massive ~11 dB(A) reduction in noise levels. As the following flow versus noise chart shows, the G2 model runs ~7-10 dB(A) quieter whilst providing the same levels of airflow through the radiator:

When comparing the round-frame NF-A14x25r G2 against the round-frame NF-A15 on the NH-U14S heatsink, the G2 version outperforms its predecessor by a significant 2.3°C at a 320W heatload:

Just like on water cooling radiators, these significant performance gains over the previous NF-A14 can be utilised either to achieve lower temperatures or, on the flipside, be used to let the new G2 fan run slower and quieter. When measured on the NH-U14S, the G2 version can provide the same levels of airflow through the heatsink as the first-generation NF-A14 while running ~2-4 dB(A) quieter:

The NF-A14x25 G2 is, however, not only superior in higher impedance applications like heatsinks or water cooling radiators, it also provides superior performance than the original NF-A14 in low impedance applications like PC case cooling. At a flow resistance typical for PC chassis fans, the G2 version produces around 13% more airflow:

As with heatsinks and radiators, the superior case cooling performance of the G2 fan can also be converted into a decisive noise level advantage: In order to achieve the same levels of airflow through a chassis as the first-generation NF-A14, the G2 version can be run at significantly lower RPM speeds, which will result in a typical 2-3 dB(A) improvement in noise levels.

In sum, the NF-A14x25 G2 and NF-A14x25r G2 provide substantial improvements over their predecessors in all applications, enabling customers to either achieve better cooling performance or lower noise levels. The improvements are particularly significant on water cooling radiators where the NF-A14x25 G2 offers a massive boost in efficiency compared to the venerable NF-A14.

NF-A14x25(r) G2 aerodynamical innovations: The keys to its superior performance

The NF-A14x25 G2 succeeds the award-winning NF-A14 and, at the same time, builds on the technological innovations of the ground-breaking NF-A12x25 such as the use of Sterrox® LCP, an ultra-tight tip clearance and its strongly swept nine blade impeller design. However, the NF-A14x25 G2 isn’t simply a 140mm version of the NF-A12x25, but rather represents a further refined, second-generation implementation of this design approach. In particular, the aerodynamic design of the NF-A14x25 G2 is characterised by the introduction of the novel Progressive Bend impeller, the Centrifugal Turbulator hub and the addition of winglets, all of which work together in order to enable a breakthrough in airflow-to-noise efficiency compared to the original NF-A14.

Progressive Bend impeller

The NF-A14x25 G2 features a unique Progressive Bend impeller with Flow Acceleration Channels and winglets. Whereas the NF-A12x25’s nine impeller blades are bent relatively continuously, the NF-A14x25 G2’s blades are swept backwards close to the hub and progressively bent forward further out, which results in a distinct, almost kink-like shape. Working in tandem with the Centrifugal Turbulator hub, this design not only helps to push more air towards the outer blade areas where efficiency is higher, but also assures maximum lift and near uniform loading across the entire blade span. Since the absolute speed of fan blades becomes lower and lower closer to the hub, aerodynamic performance is highest near the tips of the blades and lowest near the hub. By driving more air outwards to the higher efficiency zones, overall efficiency can be increased. However, care must be taken to maintain as even as possible loading over the entire length of the blades in order to avoid flow separation and air leaking back through a low-performance central region in applications with high back pressure such as heatsinks or radiators. The NF-A14x25 G2’s novel Progressive Bend impeller strikes a perfect balance between driving air outwards for maximum efficiency gains and keeping a near uniform loading to ensure consistent performance in high impedance applications. Last but not least, both the shape and the profile of the NF-A14x25 G2’s blades have been carefully fine-tuned to enhance aerodynamic lift, which gives its P/Q curve an extra push in the critical mid-section and thereby also contributes to the fans superior performance on heatsinks and radiators.

Centrifugal Turbulator hub

The second novel feature of the NF-A14x25 G2’s impeller is the new Centrifugal Turbulator hub. By acting as a turbulator, this novel design measure improves flow attachment in the hub region, which, in return, enables the fan to draw in air more efficiently. At the same time, the centrifugal driving motion of the Centrifugal Turbulator Hub works in tandem with the Progressive Bend impeller design to push air outwards from the hub area where efficiency is low due to the slow rotational speed towards the outer, high-efficiency zones of the blades, thereby increasing overall efficiency by optimising fluid distribution across the impeller area.

Figure 3: Centrifugal turbulator hub pushing air outwards

Winglets

The third novel aerodynamic design measure that distinguishes the NF-A14x25 G2 impeller from the NF-A12x25 is the addition of winglets. Generally, winglets can help to reduce tip vortices that are caused by the pressure differential between the suction and the pressure side of the fan blades. However, using winglets also bears the risk of reducing efficiency due to extra fluid displacement in high velocity regions, which can often outweigh the benefits of reducing tip vortices. Navigating through these challenges, the NF-A14x25 G2’s small winglets have been carefully honed to provide consistent efficiency gains and to act in concert with the Progressive Bend blade geometry, Flow Acceleration Channels and AAO frame.

In addition to its aerodynamical innovations, the NF-A14x25 G2 is also the first fan to use Noctua’s next-generation etaPERF™ motor as well as the new SupraTorque™ feature, both of which also contribute to its superior performance. Please follow the links to learn more about these features:

etaPERF™
SupraTorque™