Non-isothermal wicking in polymer sintered bead wicks: Experimentation, analytical solutions, and numerical validation

Abstract

Though models and applications abound for spontaneous imbibition of liquids into porous media (also called wicking), this is perhaps the first attempt to propose (and rigorously test) any model under non-isothermal conditions. This paper evaluates non-isothermal wicking phenomena through experiments, theoretical models, and numerical simulations. Experiments measure the wicking height of hexadecane in a heated beaker with a polypropylene wick at room temperature. An analytical solution predicts the wicking rate based on temperature-sensitive liquid properties, such as viscosity, surface tension, and density. Three temperature models are introduced: Liquid Temperature Model, Average Temperature Model, and Dynamic Temperature Model. The first two models incorporate temperature-induced changes in liquid properties but have limitations. The Liquid Temperature Model overestimates wicking height, while the Average Temperature Model improves predictions but still faces challenges. The Dynamic Temperature Model, using numerical simulation, accurately calculates fluid properties at dynamically determined temperatures, leading to better predictions of wicking height. Comparisons with experimental data show increasing accuracy across the three models. The Dynamic Temperature Model also successfully demonstrates temperature transitions in the wick observed through thermal imaging.