Overclocker der8auer Cuts Ryzen 7 9800X3D Temps by 19°C With 110cm 3D-Printed Chimney
A passive cooling experiment demonstrates the power of the 'stack effect'—and why it remains impractical for standard PC cases.
German overclocker Roman 'der8auer' Hartung has demonstrated that a massive vertical structure can significantly cool a high-performance CPU without a single moving part. By utilizing a 110cm 3D-printed chimney, Hartung reduced the temperature of an AMD Ryzen 7 9800X3D from over 90°C to 71°C.
To conduct the experiment, Hartung mounted a tower constructed from interlocking 3D-printed PLA funnel segments atop a fanless 240mm radiator on a water-cooled test bench. To ensure a controlled thermal environment, the Ryzen 7 9800X3D was capped at a constant 100 watts. The resulting 19°C drop in temperature was achieved entirely through natural convection, removing the need for mechanical fans to move air across the radiator fins.
The Physics of the Stack Effect
The experiment relies on the 'stack effect,' a principle of natural convection where heated air becomes less dense and rises. This upward movement creates a pressure differential that pulls cooler air in from the bottom of the structure. While this concept is common in architecture and has been utilized in niche PC chassis like the SilverStone Raven series, it is rarely used for primary CPU cooling because the height required to generate meaningful airflow is typically too great for a desktop.
Hartung's testing showed that height is the critical variable for success. Incremental tests revealed that adding a mere 10cm to the structure had a negligible effect, shaving off only half a degree. However, a 30cm tower was enough to reduce water temperatures by approximately 5°C, proving that a minimum vertical threshold must be met before the pressure differential becomes effective.
The Practicality Gap
Despite the impressive temperature drop, the experiment highlights the physical limitations of passive cooling for modern silicon. According to reports from Archyde, a standard 55cm case with a 20°C room and 40°C interior generates only 0.4 Pascal of static pressure—far too little to cool a high-TDP chip effectively.
The necessity of a 110cm vertical structure to achieve a 19°C reduction underscores why active cooling remains the industry standard. Fans create the necessary pressure differential to move large volumes of air in a fraction of the space required by a passive chimney. For the average user, a meter-tall plastic tower is an impossible addition to a workspace.
What's Next
While the 110cm chimney serves as a successful proof of concept for natural convection, it is unlikely to influence mainstream chassis design. The experiment instead serves as a benchmark for the thermal limits of passive systems. Future developments in high-efficiency passive cooling will likely require new materials or radically different heat-spreading geometries to overcome the height requirements demonstrated in Hartung's test.