Design of flow control device for dynamic cold plate and optimization of servers to decrease junction temperature of heat sinks

Abstract

Electronics cooling research is facing the challenges of high heat flux removal and increased pumping power. Not much attention has been focused related to server and module level cooling. The continued increase in heat fluxes at the chip level due to new and robust technology nodes following Moore’s law is starting to push the limits of air cooling and especially for high end servers. An alternative to air cooling is liquid (water and oil immersed) cooling.

The optimized dynamic cold plates that use water as the cooling fluid have shown over 28 % and 52% of reduction in pumping power and average temperatures across the module respectively. In all dynamic cold plates, flow control device have to be used. Our first generation state of the art flow control devices required dampers, actuators, sensors, transducer and control module. This approach made the system complex and reduced its reliability as it required integration of N number of elements. Hence a new method to overcome this challenge is proposed. A passive system is designed for temperature control. Various materials are shortlisted and design parameters to have a reliability for 10^7 cyclic loading are considered.

For oil cooling 3rd generation Open Compute servers have been utilized. Optimization of heat sinks, server orientations and channels are done to decrease the junction temperature for oil-Immersed servers. The resultant effect of using mineral oil and these optimizations is that the high-end servers can have much higher heat flux density nevertheless maintain its junction temperature under acceptable limits.