The meteoric growth of social networking involvement along with cost-effective cloud based computing business models are just two reasons why data center power consumption is growing at an alarming rate. Dwindling global energy resources mandate that these data centers be more efficient, especially as our dependence and demand upon them grow. As the data center demand grows, components will be designed with reductions in volume and increases in processor speeds, resulting in increases in heat fluxes which two-phase liquid immersion techniques offer the potential of dissipating. The proposed experimental facility seeks to illustrate how these demands can be met through the integration of a small form factor line replaceable cartridge which contains heated elements meant to simulate components within a high performance computing unit. The facility also consists of thermal support equipment used for heat extraction and rejection to ambient much like one would find in a liquid cooled data center, such as a chiller, fluid pumps, etc. One way to effectively characterize the efficiency of a thermal design technique is to quantify the thermal resistance, and subsequently minimize it as much as possible. Incredibly low module level thermal resistances have been achieved, on the order of 0.13 K/W under pool conditions and as little as 0.10 K/W when flow is introduced within the electronics housing. Trends of the cartridge’s thermal resistance have been explored as exterior chilled water temperatures are varied, over several surface enhancements along with the variation of external chilled water and internal dielectric fluid flow rates. As has been noted by several authors in their study of immersion cooled modules, a condensation limit has been found and trends upon it associated with varying the previously mentioned parameters have also been documented. The effect upon thermal performance of diverting the flow over the primary heating elements in various ways has been explored through the use of Particle Image Velocimetry (PIV). These techniques have been used to illustrate how a new dielectric fluid flow distribution design resulted in increased mass flow rate over critical components within the cartridge.
Energy Performance Testing of Asetek's RackCDU System at NREL's High Performance Computing Data Center