A structural figure of merit for liquid film boiling heat transfer performance on micro/nano-structured surfaces

With the rapid development of high-power electronics and energy systems , thermal management has become increasingly important. Capillary-driven liquid film boiling on micro/nano-structured wicking surfaces shows great promise in dissipating high heat flux at a low surface superheat. However, previous models for the heat transfer coefficient (HTC) of liquid film boiling generally involve complex integral-differential calculations of heat conduction , nucleate boiling , and evaporation through the solid-fluid matrix of micro/nano-structured surfaces. In this study, a structural figure of merit is proposed as a simple index to evaluate structure-dependent HTC of liquid film boiling. This figure of merit considers general structural characteristics of hybrid micro/nano-structures, including effective micropore radius, thickness, and porosity of the wick, and the nanostructures covering the wick solid skeleton, and thus it is applicable for various micro/nano-structured surfaces. Moreover, a record-high HTC of ∼392.0 kW/m 2 K in liquid film boiling is demonstrated on a copper foam surface with a high structural figure of merit under a heating area of 10 × 10 mm 2 . The structural figure of merit can be a useful guide for surface design. • A simple HTC model for liquid film boiling heat transfer on micro/nano-structured wicking surfaces is developed. • A structural figure of merit is established to guide the design of wicking surfaces for enhanced HTC in liquid film boiling. • A record-high HTC of ∼392.0 kW/m 2 K is demonstrated on a copper foam surface with a high structural figure of merit of 2.82.