Helping Microsoft keep their cool

While conventional cooling dominates datacenters today, immersing servers in a non-conductive, low boiling point fluids such as 3M™ Fluorinert™ delivers far greater cooling performance, more consistent cooling distribution across server components, and it gives greater protection against hot spots that can significantly shorten the life of server components.

With a boiling point of just 50°C, Fluorinert™ readily transitions from a liquid to a gas, before being cooled by a condenser where it returns to liquid form and repeats the cycle. If air is introduced into the system, perhaps when the server enclosure is opened for maintenance, the performance of the condenser is reduced, with a corresponding adverse effect on the system’s overall efficiency.

To verify the principles at work, we designed and constructed a test rig to act as a scale model that incorporated all major components, with a boiler to simulate the heat load produced by the server. The rig included a species separator that takes advantage of the difference in density between the Fluorinert™ vapor and the air to be removed from the system.

Design work was then carried out using advanced computational fluid dynamics (CFD) models, running transient simulations of the gas and liquid flows. We used Schlieren photography on the test rig to visualise the airflow through the species separator, validate the CFD results and refine the design to optimise the removal of the unwanted air.