Evaporation from porous structured surfaces is encountered in a variety of applications including electronics cooling, desalination, and solar energy generation. Of major interest in the design of thermal systems for such applications is a prediction of the heat and mass transfer rates during evaporation from these surfaces. The present study develops a figure of merit (FOM) that characterizes the efficacy of evaporative heat transfer from microstructured surfaces. Geometric quantities such as the contact line length per unit area, porosity, and contact angle that are independent of details of the surface structure are utilized to develop the FOM, allowing for flexibility in its application to a variety of structured surfaces. This metric is calibrated against an evaporative heat transfer model and further benchmarked with evaporation heat transfer data from the literature. The FOM successfully captures the variation in evaporation heat transfer coefficient across different structures as well as the optimum dimensions for a given structure, and therefore can serve as a tool to survey available structures and also optimize their dimensions for heat and mass transfer enhancement.

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M. Bongarala, H. Hu, J.A. Weibel, and S.V. Garimella, A figure of merit to characterize the efficacy of evaporation from porous microstructured surfaces, International Journal of Heat and Mass Transfer 182, p. 121964, 2022