YouTuber der8auer set out to test whether natural convection, rather than fans, could meaningfully cool AMD's Ryzen 7 9800X3D, a CPU known to run hot due to its 3D V-Cache design acting as a thermal blanket. Using a water-cooled test bench with a 240mm radiator, der8auer built a series of 3D-printed chimney enclosures designed to stack the radiator's warm air and exploit the 'stack effect'—also called the chimney effect—where warm air inside a chimney is less dense than surrounding air, creating a pressure difference that pulls in cooler air from below and pushes warm air out the top.
The experiment started small: a 10cm chimney barely worked, dropping temperatures by about 0.5°C. Adding a 20cm section to bring the total to 30cm improved results further, lowering the water temperature by about 5 degrees (from 61°C) over a 30-minute stabilization period, though a fog machine test showed little visible airflow difference at this height.
The real breakthrough came when der8auer added four more 20cm sections, bringing the chimney to a total height of 110cm—reportedly nearly reaching his ceiling. At this height, temperatures dropped rapidly; the water hit 50°C within five minutes, and a fog machine demonstration clearly showed air being actively pulled through the chimney and radiator as if fans were present, despite none being used.
With the CPU previously peaking at 90°C, the 110cm chimney setup brought temperatures down to 71°C as measured by HWiNFO—a 19°C reduction achieved entirely through passive airflow. Der8auer said he did not expect such dramatic results from the experiment.
Both sources note the significant practical limitation of this approach: the towering chimney assembly cannot fit inside any standard PC case and can only be used on an open test bench with substantial vertical clearance. Der8auer also pointed out that modern PC fans exist precisely to create the same kind of pressure differential more efficiently and practically, meaning the chimney method serves more as an interesting demonstration of physics than a viable everyday cooling solution.