Computational and Experimental Validation of a Vortex-Superposition-Based Buoyancy Approximation for the COMPACT Code in Data Centers

Abstract

A simplified model and GUI package, named COMPACT (Compact Model of Potential Flow and Convective Transport), has been developed in previous years to provide a fast alternative to full computational fluid dynamic (CFD) thermofluidic models for a variety of data center applications. These include, but are not limited to, use as a first-order design tool, a potential improvement to plant-based controllers, and an initial guess for complex CFD solvers. COMPACT applies convective energy transport equations to a computed potential flow field to approximate a flow and temperature field, taking 30 s or less for a commercially available laptop to characterize a 7700 cell room. Previously, the results from this model were compared to experimental measurements taken from a data center at Hewlett-Packard Laboratories (HP Labs) in Palo Alto, CA. High localized temperatures in the model led to the conclusion that recirculation and buoyancy were contributing excessively to error in the model. This paper proposes a method of vortex superposition to account for these effects, in which locations with high temperature in the original model are analyzed and a corrective flow field consisting of Rankine vortices is superimposed on the solution. This approach is tested with further experimental measurements taken from the data center at HP Labs, as well as conventional commercially available CFD. These newer results show a marked decrease in mean deviation of the model from measured temperatures, as well as elimination of the highly localized temperatures which afflicted the original COMPACT results. The vortex superposition model is also “tuned,” with vortex strength optimized for multiple test cases at varying levels of recirculation.