Thermal resistance, evaporative and convective performance of protective clothing under coupled hypobaric and thermal stress: a thermal manikin experimental study

This study establishes a novel methodology for evaluating protective clothing performance under combined high-altitude and temperature stressors, addressing critical gaps in standardized thermal characterization for aviation apparel. By integrating a pressure-adaptive forearm manikin prototype with a full-body Newton thermal manikin, we systematically quantified thermal resistance (R_ct), evaporative resistance (R_et), and convective heat transfer coefficients (h_c) across three temperatures (−9 °C, 20°C, 34°C) and two altitudes (0 m, 4000 m). Results revealed significant pressure–temperature interactions (p < 0.05) for R_ct and h_c, while R_et exhibited altitude insensitivity at 20°C (p = 0.32). Notably, R_ct decreased by 0.15 m²·°C/W from −9 °C to 20°C at sea level but showed no significant variation at higher temperatures (20–34°C, p = 0.09). Multivariate regression models demonstrated robust predictive capabilities, with adjusted R² values of 0.85 (h_c), 0.76 (R_et), and 0.41 (R_ct), enabling rapid performance forecasting under documented operational profiles. The framework advances thermal science by resolving altitude-modulated convective and evaporative dynamics, offering direct applications in cockpit thermal management and adaptive garment design for extreme environments. This work bridges experimental and computational paradigms, reducing reliance on costly validation trials while enhancing predictive accuracy for multi-stressor scenarios in aerospace and occupational safety contexts.