Der8auer’s 110 cm chimney cuts Ryzen 7 9800X3D temperature by 19°C without radiator fans
© Der8auer Overclocker der8auer has tested whether a large vertical chimney can replace the fans attached to a PC radiator. His modular 3D-printed design reduced the reported Ryzen 7 9800X3D temperature from 90°C to 71°C.
The test system still used a water-cooling pump to circulate coolant. Only the radiator fans were removed. The chimney was mounted directly above the radiator to create airflow through natural convection.
A taller chimney produced stronger airflow
The radiator initially struggled to remove heat without fans, with the coolant reaching around 61°C. A fog machine also showed little air moving through the radiator on its own.
© Der8auer Der8auer started with a 10 cm chimney section. This produced only a small improvement of around 0.5°C. Extending the structure to 30 cm lowered the coolant temperature by another 5°C following a 30-minute stabilization period.
He then added four more 20 cm sections, increasing the total chimney height to 110 cm. The coolant temperature quickly dropped below 55°C and reached approximately 50°C after five minutes. Fog released under the radiator was visibly pulled through the cooling fins and up the chimney.
© Der8auer 
© Der8auer Natural convection replaces radiator fans
The design relies on the stack effect. Warm air inside the vertical duct becomes less dense and rises. This creates lower pressure near the radiator and draws cooler air through its fins.
The 110 cm structure is not a practical replacement for fans inside a standard desktop PC. The experiment does show that chimney height can generate enough natural airflow to cool a high-end processor through a water-cooling radiator without attached fans.
I guess it’s easy to see why such a cooling method isn’t used in modern PCs. It would take up too much space, and fans are simply more efficient.
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