Topology optimization of flow distribution zones mitigating preferential flow in large-scale PEM electrolyzers

Non-uniform fluid distribution significantly limits the performance and lifetime of large proton exchange membrane (PEM) electrolyzers, as conventional flow field designs struggle to balance the competing requirements of high uniformity and low pressure drop. This study proposes a multi-stage, multi-objective topology optimization approach, using flow uniformity and pressure drop as co-optimization objectives, to design a novel, high-efficiency flow distribution zone structure for PEM electrolyzers. A full-scale, three-dimensional, two-phase, non-isothermal numerical model was developed to quantitatively evaluate the overall performance of the new distribution zone structure in terms of fluid distribution, multi-physics field uniformity, and electrolysis efficiency. Results show that the topology-optimized distribution zone flow field (TDZFF) effectively balances longitudinal and transverse flows, mitigating the non-uniform flow phenomena caused by preferential flow effects. Compared with the conventional manifold-type distribution zone flow field (MDZFF) and the dot-array-type distribution zone flow field (DDZFF), TDZFF improves flow uniformity by 89.80 % and 46.18 %, respectively, while reducing the pressure drop by 43.73 % and 32.86 %. The enhancement in flow uniformity further improves the uniformity of liquid saturation, current density, and temperature distributions. Moreover, TDZFF establishes pressure differentials between adjacent channels to induce in-plane flow, thereby enhancing under-rib mass transport. Owing to the synergistic improvements in multi-physics uniformity and mass transfer, TDZFF achieves electrolysis efficiency gains of 9.37 % and 5.11 % over MDZFF and DDZFF, respectively, at an operating voltage of 2.1 V.