Temperature Field Prediction of Polypropylene Yarns in Fabric-Based Evaporators for Solar Seawater Desalination

Abstract

To accurately predict the temperature field in the horizontal segment of polypropylene yarns for solar-driven seawater desalination fabrics, this study performed experimental tests and modeling analysis. 900D polypropylene yarns were prepared to build a temperature test system, with data measured by an infrared thermal imager. A multiphysics coupling temperature field prediction model was developed as the core work: the unsteady conduction-convection coupled heat transfer control equation of yarns was derived, the 1D Richards equation was adopted for capillary liquid transport characterization, and the interfacial evaporation rate quantification model was coupled. The governing equations were iteratively solved after steady-state transformation, spatial discretization and second-order central difference discretization. Experimental verification showed high consistency between model predictions and measured data (RMSE= 0.92, average relative error=2.01%), which accurately reveals the gradual rise of yarn temperature from the water supply end to the evaporation far end. The study also analyzed model limitations such as idealized assumptions and parameter source issues, and proposed optimization directions including multi-dimensional modeling and experimental measurement of key parameters. It clarifies the essence of heat transfer before constructing the temperature field model, accurately reveals the heat and mass transfer correlation at the yarn scale, and provides a theoretical basis for the performance improvement of fabric-based evaporators.