Noctua's first liquid cooling prototype uses the thermosiphon principle
Now that’s news we didn’t expect from Computex 2024: Noctua, possibly the most famous coolers and fans company, has presented a liquid cooler. What’s unusual is that Noctua is focused on silent operation (which liquid cooler pumps tend to have a problem with) and reliability, and has insisted on not making any AIO liquid coolers, until now. Noctua’s liquid cooler, however, takes a different route than usual.
There are two (at least) complaints about liquid coolers. Firstly, potentially shorter lifetime and more susceptibility to problems such as clogging with sediments, leakage of liquid into the computer. Compared to that, air coolers are basically work forever and you just need to replace the fan on them if it fails, at worst.
The other problem is that the pump in the liquid coolers is always working. So while at full load they may be quieter than an air cooler due to the efficiency with which the liquid dissipates heat (although the best Noctuas and similar coolers are outperformed only by the better and more expensive AIOs), when the CPU is idle there is often a problem with the constant whine of the pump pumping the liquid in the closed loop.
And you’ll simply hear it all the time the computer is on. It’s a sound that can be quite annoying at night or while watching a movie, and you can’t get rid of it, whereas with an air cooler, a good fan like the NF-A12x25 fan can be regulated to an almost completely inaudible level, or you can even use a semi-fanless cooler to turn the fans off at low load. That’s quite possibly why Noctua hasn’t tried to make its own AIO coolers until now, although you can of course buy and fit its fans to one, and the company is actually actively working on making them suitable and good for that role.
Thermosiphon AIO liquid cooler completely without a pump
However, at Computex 2024, Noctua has now revealed its first liquid cooler, that could eliminate the latter problem entirely (and mitigate the former), so it could compete with the air champions in levels of quiet it can reach. It is in fact an AIO cooler without a pump, in which the liquid circulation is not forced by any moving-parts mechanism. The circulation could theoretically still produce some noise (similar to water flowing in your home heating), but that would most likely be very faint through the braided tubing and might not be audible outside the case, especially since the flow would probably be relatively slower.
Noctua also shows other new products at Computex 2024: The Noctua NH-D15 G2 in three variants. And new A12 fans
This cooler uses the so-called thermosiphon principle (it is said to be using a two-phase thermosiphon cooling) and Noctua is working with Calyos on the development. The principle is that instead of a pump driving the liquid, it uses the spontaneous flow that is caused by differences in temperature and thus in the density of the liquid, these differences and pumping will be created simply by the processor heating up the liquid.
The thermosiphon AIO cooler has a classic block mounted on the CPU, in which the liquid is evaporated by heating (it takes advantage of the fact that evaporation absorbs a lot of heat – the latent heat of phase-change (evaporation in this case) – which works much better than just heating the liquid by a few degrees). The warm vapor rises, which the radiator takes advantage of by passing it through the tube to the radiator. This means radiator will probably always have to be fitted above the CPU. In the radiator, the vapor is cooled and condensed by contact with the fins, and is collected from the radiator through the tubing by the outlet terminal (which, according to the diagram, is placed low so that the liquid drains out on its own, while the inlet terminal bringing in the vapor is attached higher) and is taken back down to the block on the processor to repeat the cycle.
It can be said that thermosiphon cooling uses a very similar effect to heatpipes, commonly used on all air coolers today. However, the cooler relies on gravity, and when mounting it you need to mount the radiator in the top part of the case above the CPU, but you will also probably need to watch the correct orientation of the block relative to the CPU, i.e. so that the outlet is higher and the inlet lower. In a classic tower case this is something acceptable in exchange for the benefits of this principle. You just have to remember that the computer case should be standing up straight, and not lie it down on its side.
Competitive performance, but peerless noise levels?
This pump-less loop should have an advantage in reliability besides the quiet operation, where the only noise will be from the fans (made by Noctua of course) mounted on the radiator. A significant part of AIO and liquid cooler failures is caused by the pump being a moving part. Here the evaporator in the block on the CPU will be completely free of moving parts, so the problems associated with the pump – but also the vibrations caused by it – are eliminated. This cooling could therefore be a very pleasant for your ears. Thanks to the liquid principle, it could perhaps even be quieter than competing air cooler, plus it will have the advantage that the heat from the radiator will be immediately extracted of the case, given the mounting of the radiator into case’s exhaust panel.
Noctua states that their goal is to achieve performance that is similar to a regular AIO with an active pump. It’s probably clear that it’s going to be harder to do that with spontaneous flow, so it’s not going to be an easy task, and a cooler like this will probably always be at a disadvantage against the most powerful AIOs with pumps and forced circulation, tuned for maximum cooling performance. A thermosiphon AIO, on the other hand, would provide quieter operation as a benefit, so there is likely room in the market for both types.
The cooler shown is still a prototype, the company refers to it as a “development project”. So it’s not something that will be available for purchase this year or next year, remember for example the relatively long time between the first introduction of the NH-P1 passive cooler and its release. It could be similar here. However, this concept looks like something that should be worthwhile, so hopefully the development will turn out well.
It is probably worth mentioning that thermosiphon liquid cooling is not completely new. It is used by IceGiant coolers (they do not have the format of a block and a separate tube-connected radiator though) and a pumpless prototype in a classic AIO form-factor was also shown recently by the German company Wieland. This is a relatively new area for Noctua, and it’s quite possible that the company won’t be the first player to the market with a thermosiphon AIO and actually won’t deliver a real product for quite a long time, because the company prides itself on releasing things only when they are deemed perfect, even if that means long delays.
Tip: Thermosiphon cooling: air cooler that beats liquid coolers?
Sources: PC Gamer, techPowerUp
English translation and edit by Jozef Dudáš
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