Cross scale study on the evaporation process of wet metallic wire mesh layer and its heat dissipation performance analysis

The surface microstructure of a copper mesh was first etched and modified to fabricate an ultra‑thin, hydrophilic wicking core capable of delivering liquid water while dissipating heat through evaporation. At the interfacial scale, a “stepwise wetting” process was for the first time revealed by high‑speed microscopic observation: liquid bridges were observed to nucleate at warp‑weft intersections and subsequently propagate across the mesh node by node, with the subsequent drying stage likewise dominated by the behavior of liquid bridges. The wetting rate of the mesh was found to accelerate with increasing mesh number, while the evaporation process was observed to intensify at higher mesh counts. At the macroscopic scale, a coupled heat‑and‑mass‑transfer model was established, demonstrating that the unsaturated evaporation process can be clearly divided into an externally controlled constant‑rate period (approximately 500 s) and an internally limited falling‑rate period. Evaporation efficiency was effectively enhanced by adopting a graded structure with finer pores at the bottom and coarser pores at the top, combined with reduced layer thickness. For saturated evaporation, the evaporative heat‑transfer coefficient was maintained stable above 30 W· m⁻²· K⁻¹ and conductive thermal resistance was minimized by keeping the stacked structure in a fully saturated state; under such conditions, the overall heat‑transfer coefficient was primarily governed by airflow conditions and structural thickness. Through interfacial‑scale visualization experiments and macroscopic‑scale numerical modeling, a cross‑scale systematic investigation of the evaporation process in moist wire‑mesh thin layers was achieved. Important guidance for the performance optimization of plate‑type heat sinks in transformers is provided by these findings.