Noctua’s been hard at work on its thermosiphon CPU cooler, with plenty of improvements that put it on level footing with standard AIO liquid coolers. The company now proudly boasts that its pumpless cooler is capable of keeping the Ryzen 9 9950X3D at reasonable temperatures without active liquid circulation.
The aim of this cooler is to provide the convenience and performance of standard AIO liquid coolers while eliminating the pump. Removing that moving part circumvents a potential point of failure, but also means no vibrations, reducing noise levels.
The thermosiphon, or two-phase thermosiphon to be exact, uses the same main parts as a liquid cooler, i.e., cold plate, tubes, and radiator, but ditches and pump to instead leverage natural fluid movement to remove heat from the CPU. Noctua has developed this approach in partnership with Calyos, an expert in two-phase cooling solutions for aviation and automotive.
The theory is that a pump is unnecessary, as we can instead rely on heat’s natural tendency to rise. The CPU heat causes the liquid to evaporate inside a sealed loop, reducing its density. Water vapour then moves up toward the condenser (radiator), where it exchanges its heat energy with the cold air. At a lower temperature, it condenses back to a liquid state, falling back down to the evaporator through the force of gravity. Unfortunately, this does mean you only install this at the top of a case.
Compared to earlier prototypes, showcased at prior Computex shows, there’s lots of improvements to highlight. For instance, Noctua has further optimised the evaporator design to improve vaporisation and hotspot-resistance, while revising condenser fin and microchannel structures to maximise condensation with the NF-A12x25 G2 fans.
Furthermore, the company has also improved the compatibility of the condenser’s inlet/outlet. There’s also new tubing materials, which offer lower permeation, reduced levels of non-condensable gases, as well as better connector sealing. To get to this stage, Noctua trialled over 400 evaporator and 25 condenser prototypes, all built over the last 12 months.
Placing the prototype cooler on top of the AMD Ryzen 9 9950X3D, with fans running at 1,800RPM, temperatures remained at a solid 82°C while pulling 230W of power. This result was only a few degrees above Noctua’s AIO liquid cooler, which as a pump at its disposal.
Noctua expects to offer a 10-year warranty with this thermosiphon cooler, with the absence of a pump bolstering reliability. However, there is potential for air to permeate in the tubes and create air pockets, impacting cooler performance. To counteract this problem, the thermosiphon uses larger-diameter tubes compared to traditional AIOs.
We should also note that Noctua believes hte final product will have a smaller evaporator, supposedly around half the size of the unit you’ve seen in the pictures above. The company expects to formally debut this cooler in Q3 2027, so that’s plenty of time to shrink down the footprint.
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