Membrane-Enabled Passive Evaporation-Diffusion Cooling for Mitigating the Water-Energy Trade-Off in Recirculating Cooling Systems

Abstract Recirculating cooling water systems (RCSs) are essential for industrial thermal management, yet their reliance on continuous water circulation and evaporation-induced makeup water imposes substantial water and energy burdens. Here, we report a passive interfacial cooling strategy by integrating polytetrafluoroethylene nanofibrous, porous membranes (PTFE NPMs) into the cooling unit of an RCS. Owing to the intrinsically low surface energy of PTFE and the interconnected micro/nanoporous fibrous architecture, the membranes exhibit robust superhydrophobicity, antiwetting stability, and efficient vapor permeability. This hierarchical interface promotes rapid outward diffusion of water vapor from hot water while suppressing liquid-water retention and penetration, thereby accelerating evaporation-diffusion-mediated heat dissipation without external energy input. Meanwhile, the tortuous hydrophobic nanochannels function as selective mass-transfer barriers, enabling vapor escape while preventing the intrusion of droplets, particulates, and contaminants, which is beneficial for maintaining circulating-water purity and reducing water consumption. In a 300 s cooling test, a conventional RCS cooled a copper disk to 47.5 °C with an average cooling rate of 0.588 °C s–1, whereas the PTFE-NPM-integrated system reduced the temperature to 44.5 °C and increased the cooling rate to 0.651 °C s–1. This work demonstrates a membrane-enabled, energy-free cooling enhancement strategy for sustainable RCSs and provides a materials platform for water-saving industrial thermal management.