Liquid cooling
AI racks pack so much power into a small space that fans and cold air can no longer carry the heat away, so water-based cooling is piped right up to the chips.
Read first: Power & cooling for AI data centres.
D1 · StoryFor young children and total beginners
AI chips get very hot, and they are squeezed close together.
Blowing air over them is like blowing on hot soup. It works for a little heat, but not for a lot.
So builders run cool water through metal plates that touch the chips, and the water carries the heat away.
Like: Cooling a hot pan under the tap instead of blowing on it.
D2 · PictureFor curious beginners
Nearly all the electricity a chip uses becomes heat. Air cooling pushes cold air through the rack with fans, but air holds little heat, so very dense racks would need more airflow than is practical.
Water carries heat far better than air. In direct-to-chip cooling, a liquid flows through a cold plate pressed onto each processor, then out to a heat exchanger. In immersion cooling, whole servers sit in a non-conductive fluid.
The newest AI systems are designed as liquid-cooled racks from the start, so a building that can only do air cooling may not be able to host them. Most liquid-cooled racks still use some air for parts such as power supplies.
Like: Cooling a hot pan under the tap instead of blowing on it.
Where it breaks: Tap water runs once and goes down the drain. Data-centre loops are usually closed: the same liquid circulates, and the heat still has to be dumped somewhere outside, by cooling towers or dry coolers, which may use water of their own.
D5 · FrontierFor experts
Open questions: how to retrofit older air-cooled buildings, which liquid approach (cold plates or immersion) wins at even higher densities, and how to reuse the waste heat rather than dumping it.
Liquid cooling can cut cooling energy, but the water story is subtle: closed loops use little, while the outdoor heat rejection can use a lot, depending on climate and design.