Study on numerical model of thermal conductivity of non-aqueous phase liquids contaminated soils based on mesoscale

Abstract

The thermal conductivity of soils is an important factor affecting the efficiency of in-situ thermal desorption remediation of contaminated sites. Restrict the selection of in-situ thermal desorption repair methods and heating parameters. The existence of non-aqueous phase liquids (NAPLs) pollutants affects the original thermal conductivity of the soils. To obtain an accurate and efficient method to study the thermal conductivity of NAPLs-contaminated soils. In the paper, the NAPLs-contaminated soils models are established by the four-parameter random generation method, and the thermal conductivity is calculated based on the Lattice Boltzmann Method (LBM). Explore the impact of NAPLs-contaminated soil model on its thermal conductivity calculation results, and propose an optimized NAPLs-contaminated soil model. Finally, the numerical simulation results are compared with the experimental results, and a large number of calculations and statistical analyses are carried out on the thermal conductivity. The results indicate that it is feasible to combine the four-parameter random generation method with LBM to study the thermal conductivity of NAPLs-contaminated soils. The calculation accuracy of the two-dimensional model of NAPLs-contaminated soils is lower than that of the three-dimensional model, while the calculation of the three-dimensional model is too time-consuming. The optimized NAPLs-contaminated soils three-dimensional model has the characteristics of high computational accuracy and efficiency. Saturation and Nz have a great influence on the calculation time of thermal conductivity. The thermal conductivity of the two-dimensional model is more sensitive to anisotropy. With the decrease of model anisotropy, the increase of saturation, and the decrease of porosity, the calculation accuracy of thermal conductivity of two-dimensional and three-dimensional models is similar, otherwise, the calculation accuracy of two-dimensional model is lower. The influence of porosity and NAPLs content on thermal conductivity should be paid special attention to when in-situ thermal desorption.