The process builds upon pool-boiling—liquid-cooling at a temperature near the boiling point of the fluid—but uses two heat-generating circuit chips together, wherein each chip alternates its voltage relative to the other.
When submerged in the coolant, the heat from one chip produces bubbles which have a recoil force that propels the chipset in one direction at a speed of one centimeter per second. This is then followed by the other chip, which propels the chipset in the opposite direction.
Sumit Sinha-Ray, one of the researchers who led the project, likens the recoil of each bubble to “jet propulsion.” The researchers also found that the recoil force has a greater arc and higher velocity when there are smaller and more numerous bubbles. Polymer-based nanofibers were supersonically blown the surface to facilitate an increase in small bubbles.
In effect, the chipset swings in the coolant to remove the bubbles. In zero-gravity conditions, this process prevents the bubbles from forming a vapor layer, which would interrupt the heating process. Thus, the bubble-recoil cooling method is an effective cooling solution for microchips in space.
If successfully applied, bubble-recoil liquid-cooling would result in powerful computing in space, which has been limited by challenges of zero-gravity. Liquid cooling is currently ineffective, since bubbles do not have buoyancy in space, and thus will stay on the submerged surface and potentially even form a vapor layer. Other available methods, such as mechanical mixing and electric fields, would also generate heat in addition to involving other complexities in terms of room and power consumption, making them infeasible.
The bubble-recoil method was developed by a team at the University of Illinois at Chicago (UIC) with funding support from NASA. Alexander Yarin, a professor of mechanical engineering at UIC, is the senior author of the study, which has been published in the journal Nature Microgravity.
For more news from Illinois, check out the winners of a contest to design an excavator cab.