Oil stain removal in woven fabrics under transient flow cycles using a ternary hybrid nano-detergent

This study computationally investigates the thermo-hydraulic performance of a novel ternary hybrid nano-detergent, formulated by dispersing ZnO (40%), CuO (30%) and magnetite Fe 3 O 4 (30%) nanoparticles at a total volume fraction of 0.5% into a water-based commercial laundry detergent, designed to provide antibacterial functionality and enhance oil-stain removal within a microscale woven fabric pore under dynamic washing conditions. A transient, three-dimensional Volume of Fluid (VOF) model coupled with species transport is employed to simulate the multiphase flow, heat transfer, and oil dissolution within a representative microscale fabric pore. The simulations incorporate four distinct unsteady inlet velocity profiles (Incremental, Decremental, Incremental-Decremental, and Decremental-Incremental) over a laminar Reynolds number range of 0.35 to 1.40. Effective thermophysical properties of the nano-detergent are calculated using classical Maxwell and Brinkman models for the dilute nanoparticle suspension (φ = 0.5%). The results demonstrate that flow kinematics profoundly influence cleaning efficiency: the Incremental-Decremental velocity profile achieves the highest time-averaged convective heat-transfer coefficient of 1181 W/m 2 ·K at Re = 1.40. Hydraulically, the Decremental-Incremental profile yields the lowest time-averaged pressure drop of 0.15 Pa at Re = 1.40, underscoring its energy-efficient character, whereas the Incremental profile induced the highest average hydraulic resistance, reaching 0.39 Pa.