Numerical modeling of quasi-static spatially-variable liquid film evaporation in oscillating heat pipes under vapor shear stress

• Vapor shear stress governs rear liquid film replenishment in OHP evaporators. • Variable heat flux behavior is predicted beyond forward-meniscus supply models. • Temperature-dependent performance differs between R134a and acetone. • Velocity-dependent liquid supply captures experimental dryout trends. • Simplified model reproduces heat transfer trends with low cost. In this work, a physics-based numerical model of liquid film supply and evaporation in the rear region of slug flow in an oscillating heat pipe (OHP) is developed. While prior models in literature have focused exclusively on liquid supply from the front meniscus region, this work introduces a new approach where vapor shear stress drives liquid distribution in the rear film, allowing for continuous liquid supply. Model predictions are validated against published experimental data from the Jet Propulsion Laboratory (JPL). Results demonstrate that rear-film evaporation may contribute significantly to overall heat transfer in OHP evaporator systems, offering an updated perspective on OHP thermal transport mechanisms.