Experimental Study of Periodic Electric Field Coupled Helical Electrodes to Improve Nanofluid Steam Generation in Solar Collectors

Direct absorption solar collectors (DASCs) are widely applied in residential heating, wastewater treatment and desalination. Although electric fields and nanofluids can enhance photothermal conversion, the performance improvements using needle electrodes and constant electric fields remain limited. Hence, the present study aims to enhance the steam generation performance of nanofluid‐based DASCs by optimizing electrode and electric field modulation. The novelty lies in combination of helical electrodes and periodic electric fields, which are introduced to replace conventional needle electrodes and constant fields, respectively. Systematic experiments are conducted under varying helical pitches, switching cycles, and solar intensity. The results demonstrate that both the helical electrode and periodic electric field significantly enhance steam generation performance. Under solar irradiance of 1000 W/m 2 , voltage of 7.5 kV and switching cycle of 20 s, the evaporation rate increases by 39.3% and the evaporation efficiency improves by 27% compared with the no‐field condition. The enhanced performance is attributed to the helical electrode's ability to generate a spatially extended and favorably oriented electric field, as well as the periodic electric field's role in intensifying nanoparticle motion, promoting bubble nucleation and coalescence, suppressing aggregation, and improving internal heat transfer. These findings provide a viable strategy for solar thermal energy systems.