Wettability-confined liquid-film convective cooling: Parameter study

An experimental investigation is conducted on the cooling of a metallic heat spreader of O(10 cm²) area with an embedded millimeter-size heat source. Specifically designed wettability patterns featuring wedge-shaped wettable tracks on the heat spreader divert an orthogonally-impinging water jet providing necessary cooling. Capillary-driven, directional, free-surface transport of the coolant is accomplished for several centimeters on the heat spreader. Sensible heat transfer is evaluated at different flow rates for various patterns and heat source to heat spreader relative positioning. Marangoni stresses arising from temperature gradients oppose the free-surface flow under certain conditions. Strategies to overcome the detrimental effects of such thermocapillary stresses are explored and analyzed in terms of cooling performance. Fundamental flow and track design parameters are explored in pursuit of increased performance and Marangoni-resilient wettability patterns. Heat removal rates of the order of 100 W/cm² are attained without phase change at coolant flow rates as low as ~1 mL/s and heat source superheats of 65^oC. The present approach opens up new opportunities for heat removing devices that rely on advective cooling facilitated by wettability-patterned metal substrates.