Elliptical pillars for the thermal performance enhancement of micro-structured evaporators

In this study, we propose and investigate the employment of elliptical micropillars as a novel evaporator wick structure to boost the performance of capillarity-driven two-phase heat spreaders through high-fidelity numerical modeling that accounts for all pertinent transport mechanisms, including thermocapillary convection. Results reveal that transforming cylindrical micropillars to elliptical ones significantly enhances the overall evaporator performance by improving the hydraulic performance associated with decreased flow resistance and boosted capillary pumping and by improving the thermal performance associated with increased contact (triple) line length. Among the scenarios tested and elliptical aspect ratios swept, it is demonstrated that the heat capacity and heat transfer coefficient can be increased by up to 350% and 52%, respectively. Overall, this study paves the way for the utilization of stretched geometries in the capillary flow direction of pillar-type evaporators by using elliptical micropillars as a demonstrator showcase.