Study on heat and mass transfer characteristics of porous media with different pore structures under continuous wave laser irradiation

Abstract

The pore structure determined by porosity and particle diameter directly influences the mass and heat transfer capabilities within porous media. The effect of different pore structures on heat and moisture transfer within porous media under laser irradiation remains unclear. This paper addresses this issue by establishing a theoretical model of continuous wave (CW) laser irradiation on unsaturated porous media, and investigates the effects of four different pore structures on heat and mass transfer through experiments and simulations. The agreement between the experimental and simulated surface temperature rise curves in the study is relatively good, indicating that the model can reflect the temperature rise patterns of sand grains with different pore structures. Different pore structures have a minor impact on the temperature distribution of the solid phase and pressure distribution under CW laser irradiation. Over time, the Nusselt number decreases continuously under CW laser irradiation, but in terms of space, the relative magnitude relationship of Nusselt numbers among samples remains unchanged. Laser irradiation enhances the Darcy velocity, primarily influenced by both the Nusselt number and permeability. Although the internal pressure generated by water phase change can promote gas flow, it is not the primary influencing factor. Additionally, the evaporation rate is positively correlated with the Nusselt number, while Darcy velocity and gas-phase space size are also important influencing factors. Overall, this work provides results on the impact of pore structures on the internal heat and mass transfer processes within porous media under CW laser irradiation, thereby offering a theoretical basis for laser soil remediation technique or related studies on the interaction between laser and porous media.