Experimental determination and finite element modeling of thermal conductivity in moist sand

The thermal conductivity of sand strongly depends on its moisture content, with wet or partially saturated sands typically exhibiting values above 1 W m − 1 K − 1 . Reliable estimates are important in geotechnical, civil, and energy engineering applications where sands act as natural or engineered heat-transfer media. In this work, laboratory experiments and finite element method (FEM) were combined to evaluate the effective conductivity of moist sand. Two buried-source configurations were tested: a U-shaped aluminum tube circulating hot water and a vertically embedded solid aluminum cylinder with internal resistance heating. The effective conductivity was back-calculated using classical conduction shape factors from the measured heat rates and temperature differences, and the same setups were reproduced numerically in two-dimensional steady-state finite element models. The U-tube analysis yielded values of 0.99– 1 . 09 W m − 1 K − 1 , while the cylinder experiment gave 1.34– 1 . 62 W m − 1 K − 1 depending on the assumed air-side heat transfer coefficient. Finite element predictions from two-dimensional steady-state surrogate models were consistent with the measured temperature levels at the monitored locations for k = 1 . 0 – 1 . 1 W m − 1 K − 1 , providing an internal cross-check of the inferred conductivity range. Together, the results indicate an effective conductivity of 1.0– 1 . 5 W m − 1 K − 1 , broadly consistent with literature values and with the measured moisture contents. The study demonstrates that simple benchtop experiments, combined with shape-factor analysis and FEM, can provide practical conductivity estimates for porous media and serve as an instructive framework for conduction problems involving buried heat sources. • Thermal conductivity of moist sand was determined experimentally using u-shaped tube and buried cylinder geometries. • Conduction shape factors were applied to back-calculate effective sand conductivity from measured heat rates and temperature differences. • Finite element models (FEniCS/Gmsh) were developed to replicate the experiments under steady conduction assumptions. • Both analytical and FEM approaches yielded consistent conductivity values of k = 1 − 1 . 5 W m − 1 K − 1 in agreement with literature data for wet sands. • The study provides a pedagogical link between laboratory measurement, shape-factor theory, and FEM simulation for conduction in granular media.