Flow field characteristics and multi-objective optimization of a rectangular gas distributor

Flow uniformity and pressure drop are key design concerns for multi-outlet gas distributors, yet their coupled optimization remains underexplored. In this study, a rectangular multi-outlet gas distributor was investigated using computational fluid dynamics (CFD) coupled with response surface methodology (RSM), with the objective of simultaneously minimizing the flow maldistribution index M and pressure drop Δ P . The outlet aspect ratio b / a , area ratio AR, and equivalent Reynolds number Re eq were selected as design variables over the ranges of 0.67–1.33, 1.0–1.8, and 5.4 × 10 4 –2.17 × 10 5 , respectively. Results show that M remains nearly constant at 0.216–0.218 within the mid-Reynolds range and only increases to 0.252 at the highest Re eq , whereas Δ P rises substantially from 4.53 to 72.51 Pa. Parametric analysis reveals that AR exerts a dominant influence on flow uniformity, while the outlet aspect ratio plays only a secondary role. Multi-objective optimization yields an optimal configuration at b / a = 0.867, AR = 1.248, and Re eq = 1.88 × 10 5 , achieving a 5.11% reduction in M with a well-balanced trade-off between uniformity and pressure penalty. Further flow-field analysis indicates that the inlet expansion induces jetting and recirculation zones, which reduce static pressure near the upstream region and consequently suppress discharge through the front outlets. These findings elucidate the underlying flow redistribution mechanisms and provide practical guidance for the geometric design and performance optimization of rectangular gas distributors in industrial applications.