Data centres at the heart of the artificial intelligence (AI) revolution could be cooled more effectively and economically with a hybrid system under development at the University of Waterloo that targets hotspots on computer chips with a single drop of boiling coolant.
The novel concept combines general immersion cooling with inexpensive deionized water and targeted spot cooling of especially hot areas with drops of costly coolant.
“It’s a division of labour,” said Dr. Sushanta Mitra, a professor of mechanical and mechatronics engineering at Waterloo. “Water is excellent at handling steady, everyday heat and the drops take care of sudden spikes.”
To deal with the enormous amount of heat generated in sprawling data centres, operators are increasingly immersing electronic components such as chips and processors in specialized coolant.
Depending on the workload, small areas in chips can get much hotter than others in a matter of seconds, causing them to slow down, age faster and undermine reliability. Coolant that simply flows by is too slow to react to the sudden hotspots.
The research team – which included Dr. Tian-Yu Zhang, a postdoctoral researcher, and PhD student Arnav Banerjee – tackled that problem by building on its previous work to encapsulate one liquid in a thin skin of another.
They selected an electronics coolant with a much lower boiling point than water. The coolant is also heavier than water, so it doesn’t mix with it and stays put when placed on a hotspot.
In laboratory testing, a single drop of coolant boiled and reduced the temperature of a simulated computer chip hotspot submerged in a tank of water by up to 17° C in 15 seconds, several times faster than conventional immersion.
“Boiling soaks up a lot of heat and the rising bubbles stir the surrounding water so it carries heat away faster,” said Mitra, executive director of the Waterloo Institute for Nanotechnology. “We get the punch of boiling, but only where and when it’s needed.”
Researchers then used their encapsulation technique to wrap coolant drops in a thin skin of silicone oil. Adding tiny, heat-conducting ceramic particles to the coating helps control how quickly the drops boil.
Researchers envision the system ultimately working in one of two ways – either coolant drops that circulate through water and activate when they hit hotspots, or drops that are delivered directly to hotspots detected by sensors.
The hybrid cooling approach also has potential applications in technologies including electric vehicles, batteries, high-powered lasers and LED lighting.
The study, A hybrid immersion cooling assisted by liquid-liquid encapsulation: A game changer for thermal management of transient hotspots , was recently published online in the Journal of Colloid and Interface Science .
Journal of Colloid and Interface Science