Optimizing thermal insulation in footwear: A numerical simulation approach with CAD modeling

This study addresses the challenge of evaluating the thermal insulation of technical footwear designed for cold environments. The aim is to develop a calculation tool to predict the thermal resistance (R, in mK/W) of new footwear models before prototypes are manufactured. The model assumes stationary heat transfer and solves the relevant energy balance equations using a finite volume approach that takes into account the heterogeneous thermal properties of footwear components. Two simulation campaigns were carried out. In the first, tests with human subjects were simulated, where the boundary conditions included a prescribed internal heat flux (60 W/m), a fixed ground contact temperature (-17 °C), and convective heat transfer to the outer surface. The second set of simulations mimicked manikin tests (UNI EN ISO 15831:2004), using fixed temperatures at the foot–shoe interface and on the floor (10 °C) and external convection. Validation with experimental data showed good agreement, underpinning the model’s ability to assess insulation performance under controlled conditions. Further simulations investigated the effects of different environmental parameters (temperature, wind speed, and ground contact) on heat loss. Statistical analysis revealed that ambient temperature had the greatest influence, explaining 37% of the total variance in heat flux, followed by ground type (22%) and wind speed (13%). This tool not only enables early assessment of thermal insulation in unbuilt prototypes, reducing reliance on time-consuming laboratory testing, but also supports detailed thermal diagnostics. It facilitates zone-specific optimization by changing the material composition and boot construction, promoting targeted design improvements under realistic operating conditions.