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

The pore structure determined by porosity and particle size will directly affect the remediation efficiency of thermal treatment on contaminated soil. To investigate the remediation capability of continuous wave laser soil remediation technology on soils with different pore structures, this paper establishes a heat and mass transfer model within unsaturated porous media under laser irradiation. Four pore structures were simulated, and the model's reliability was experimentally validated. Under laser irradiation, energy exchange between the solid and gas phases has a minimal effect on the solid phase temperature. The temperature distribution of the solid phase in the four samples is similar, with the differences primarily arising from moisture content. Interface energy exchange dominated the rise in the temperature of the gas. The intrinsic Nusselt numbers for the four samples were 3.5, 4.4, 4.9, and 6.2, respectively. Laser irradiation causes the Nusselt number to decrease over time, but the relative magnitudes of the Nusselt numbers for the four samples remain unchanged. From the perspective of solid phase temperature, the capability of laser remediation for soils with different pore structures is similar. From the standpoint of gas temperature, the Nusselt number is decisive. However, considering the complex coupling relationship between gas temperature rise and Darcy velocity and evaporation rate, the influence of water saturation and intrinsic permeability cannot be ignored. The research findings can provide a theoretical basis and analytical methods for the efficient laser remediation of soils with different pore structures.