der8auer’s 3D-Printed Cooling Chimney Cuts Ryzen 7 9800X3D Temps 19°C

A German tech YouTuber is putting a surprisingly old-school physics idea to the test in PC cooling: a tall, 3D-printed “chimney” mounted on a water-cooling radiator, tested without any fans, is reported to cut CPU temperatures dramatically.

3D-printed “chimney” cooling drops Ryzen 7 9800X3D temps by ~19°C

In a new video, der8auer explores whether the so-called chimney effect can actually help inside a PC cooling setup—specifically when fans are omitted. His results, based on his own measurements, show a major temperature reduction when a 3D-printed chimney structure is added to a water-cooling radiator.

• Test CPU: Ryzen 7 9800X3D
• Cooling setup: pump + radiator + temperature sensor at the mount; no fans
• Power control: AMD Precision Boost Overdrive (PBO) held the CPU at 100 W sustained loss during the test
• Key result: CPU temperature dropped from about 90°C to roughly 71–72°C (≈19°C difference)

For the experiment, he stacked several 3D-printed elements to simulate a chimney on the open radiator. Using multiple smaller segments, he reports that a 10 cm-tall add-on produces a slight drop in water temperature, while a 30 cm total height yields about a 6°C difference compared to the fanless baseline.

The biggest change comes with the full-height build: a chimney reaching 110 cm total height, made from four elements that together form an 80 cm tall chimney section. With that configuration, the CPU temperature readout in HWInfo reportedly falls from around 90°C to about 71–72°C. To make the airflow visible, he also used a fog machine, showing the fog being pulled in at the lower end of the radiator and traveling upward through the chimney pipes.

Does it replace case fans? der8auer says no—PC airflow is messier

der8auer cautions that the effect won’t translate one-to-one to a normal PC case. Real PC interiors typically lack a sealed chimney structure and the same extreme height. Instead, the presence of additional components and their associated airflow—especially the GPU—creates a more chaotic flow field than the controlled test rig.

His takeaway is that while the chimney effect in a case is real, it isn’t a substitute for active cooling. He argues that even a single 120 mm fan running at low speed could create a stronger pressure difference than the full chimney setup used in the video.

What to watch next

The video’s practical implication is straightforward: if you’re already using fans, their orientation may matter more than many expect, because they can reinforce an upward airflow process that’s already happening naturally. The next question for builders will be how much of the reported gains can be reproduced in real cases with different radiator placement, GPU airflow, and achievable “chimney” height.