Numerical Study on the Influence of Micro-Geometric Characteristics of Scrapers on Flow Field Distribution in Wiped-Film Molecular Distillers

Conventional wiped-film molecular distillers (WFMDs) often show limited hydrodynamic renewal and mixing when processing high-viscosity materials because of liquid pooling and weak secondary flow. This study investigates a novel grooved scraper design for a wiped-film molecular distiller handling an ethylene glycol/glycerol mixture (42.0 mol% ethylene glycol; density 1196.0 kg/m3; dynamic viscosity 0.222 Pa·s), used here as a representative high-viscosity, heat-sensitive system. Three-dimensional multiphase CFD simulations were performed to examine the combined effects of groove width (2.0–10.0 mm) and scraper tip angle (30–75°) on flow behavior. The results show that a groove width of 7.0 mm increases vorticity gain by 9% and wall shear stress gain by 20% relative to the inline scraper baseline. The grooved geometry generates periodic shear disturbances, promotes radial secondary flow, and strengthens turbulent mixing. A balance between radial mixing enhancement and axial transport continuity is required. Among the tested angles, a tip included angle of 45° produces the highest average vorticity magnitude and more coherent vortex structures. These findings clarify the hydrodynamic regulation mechanism of scraper micro-geometry and support its use as a process-intensification strategy for distiller parameter selection.