A Tissue-Stratified Anatomic Three-Dimensional Heat Transfer Model for Evaluating Human Body Thermoregulatory Responses to Extreme Metabolic and Environmental Stressors

In this study, an improved three-dimensional (3D) human thermoregulation model was developed. A stratified model of the segmented human geometry was introduced, characterizing distinct tissues and organs to activate their specific thermal responses and interactions. The main trunk geometry was modified to improve reliability and support applications, such as personal cooling systems. The model accounted for heat transport via blood arteries and emphasized changes in skin thermal conductivity to simulate vasodilation and vasoconstriction mechanisms. Additionally, the thermal effects of direct solar radiation on the human body were integrated into the mathematical framework. The model was validated using documented experimental data across various hot and cold environmental conditions and compared with recent 3D models. Results demonstrated that the enhanced model achieved better agreement with experimental data than existing unstratified segmented models. Improved stratification captured temperature variations across adjacent tissue layers, providing more accurate peripheral and core temperature distributions. A case study investigated strenuous military tasks performed under extreme heat, yielding significant medical insights. This advanced stratified anatomic model serves as a robust tool for predicting human thermoregulation during diverse activities, offering detailed core and skin temperature distributions. Furthermore, the modified sweepable geometry may enhance numerical methodologies for future 3D studies.