A der8auer chimney cooling experiment has shown a Ryzen 7 9800X3D running 19 degrees Celsius cooler after the modder mounted a 110cm 3D-printed tower on top of a radiator. The point was not to build the next sensible PC case. It was to test whether natural convection, usually too weak for serious PC cooling, could be made useful by giving warm air a tall path upward.
In a video demonstration, der8auer used the stack effect, also called the chimney effect. The mechanism depends on air density differences caused by temperature and humidity. Warmer air rises through the chimney, and that movement creates a pressure difference that draws cooler air in from below.
PC builders normally use fans because mechanical pressure is compact, predictable and not fussy about whether the computer has a plastic smokestack bolted to it. der8auer’s test asked a narrower question: if the radiator had enough vertical ducting above it, could buoyancy move enough air to matter?
How did der8auer's chimney cooler work?
The test bench used water cooling with an AMD Ryzen 7 9800X3D. der8auer added a temperature probe at the water-cooling fittings to watch coolant temperature, and he used a fog machine to make airflow visible around the radiator.
With no fans installed, the fog test showed the radiator was not meaningfully pulling air through itself. Heat leaving the radiator had to depend on natural convection, which in a normal open setup is weak and messy.
The first chimney section was 10cm tall and 3D printed. According to der8auer’s measurements, that short duct barely changed the system, but it still moved temperatures downward by about 0.5 degrees Celsius. The result was small, yet it showed the setup was not doing absolutely nothing.
At a coolant temperature of 61 degrees Celsius, der8auer added another 20cm section, bringing the chimney to 30cm. After a 30-minute stabilization period, the water temperature fell by another 5 degrees. The fog machine, however, still did not show a dramatic airflow change at that height.
The larger test used four additional 20cm sections, producing an 80cm extension and a total chimney height of 110cm. Once that taller structure was attached, der8auer reported that temperatures dropped below 55 degrees Celsius quickly. About five minutes later, the coolant reached 50 degrees Celsius.
The fog demonstration changed more clearly at the full height. When der8auer released fog underneath the radiator, the air visibly moved upward through the chimney, giving the radiator a passive draft that resembled fan-assisted airflow.
What did the Ryzen 7 9800X3D temperature show?
der8auer reported that the Ryzen 7 9800X3D had previously reached 90 degrees Celsius in the test. With the full 110cm chimney installed, HWiNFO showed the CPU at 71 degrees Celsius. That is the 19-degree drop from the experiment.
The result does not make fans obsolete, and der8auer tied the demonstration back to why fans are used in normal PCs: they create the same useful pressure difference in a far more practical package. The chimney worked, but it also required turning a PC cooling loop into a meter-tall physics prop.
This story draws on original reporting from Tom's Hardware.
