Effect of Flow Guide Integration on the Thermal Performance of High Performance Liquid Cooled Immersion Server Modules

Liquid immersion cooling technology, currently in its nascence as a commercially available solution for data center installations, is growing in popularity as the power density of next-gen electronics necessitates a matriculation to thermal management techniques capable of handling incredibly high heat fluxes reliably and efficiently. The use of boiling and single-phase convective solutions using dielectric fluids can result in dramatic reductions in chip temperatures, thus increasing reliability. The latter method is growing in popularity faster than the former but, as both of these approaches gain acceptance, packaging engineers will require insight into how coolant is distributed throughout the enclosure for either solution. More specifically, analytical and experimental techniques will be required to ascertain how thermal performance and system efficiency of more critical elements, such as processor chips, are affected by the auxiliary components, heated or not, that must exist within a computing device. These supplemental components, whether entirely passive or modestly heated, if placed strategically can be integrated in such a way to improve the thermal performance of the system by guiding the coolant through the liquid filled enclosure. To this end, flow guides, which simulate these auxiliary components, have been integrated into a small form factor high performance server module. The relationship between the surface temperature and the power dissipated by the primary heated elements within the device has been explored as well as the pressure drop experienced by the coolant flowing through the enclosure. Power dissipations near 450W have been achieved at a surface temperature of approximately 75°C with the use of flow guides, a near 50W improvement over previous results. Furthermore, this value was attained at a modest pressure drop of 0.71 psi for the dielectric fluid flowing through the cartridge. Slightly over 300W of power dissipation was achieved at an even lower pressure drop of 0.13 psi at a similar operating temperature. Pool boiling results have shown that passive elements can have a significant impact on thermal performance. Reductions of nearly 50W in the maximum power dissipation achieved have been shown when the largest flow guide is integrated. A PIV analytical method is proposed and applied to the current experimental facility to assess the effectiveness of the flow guide design proposed.