Effects of walking activity on micro-environment heat convection and thermal comfort in chemical protective clothing

Walking exerts complex influences on heat transfer within the micro-environment of chemical protective clothing (CPC), and consequently impairs wearers’ thermal comfort. Existing studies lack approaches for the rapid estimation of heat transfer and thermal comfort. To elucidate this issue, an intermittent meditation-walking-meditation protocol at 2 km·h⁻¹ under two ambient temperatures: 25 °C and 40 °C was performed by human-subject trials. Micro-environment ambient temperature and relative humidity at chest and upper arm were measured, as well as skin temperature and subjective perceptions. Furthermore, dimensionless analysis (Nusselt number (Nu), Reynolds number (Re), Richardson number (Ri)) quantified convective dynamics and evaluated thermal comfort vote (TCV). The results showed that during walking at 40 °C, the chest skin temperature and micro-environmental temperature at the chest CPC inner boundary increased by 2.9 °C (34.2±0.4 °C → 37.1±0.2 °C) and 12.3 °C (25.3±1.6 °C → 37.6±0.6 °C), respectively. While corresponding increasements were only 1.5 °C and 3.9 °C at 25 °C. Walking induced forced convection in micro-environment and differed across body segments: turbulent flow (Re: 3500—3650) was evaluated at the chest with the micro-environmental thickness of 70—150 mm, while laminar flow at the upper arm (thickness 5—25 mm). Furthermore, synergistic heating from the environment and skin narrowed the micro-environmental temperature difference, weakening natural convection. This lowered the chest Nu and dropped TCV to -1.88. Finally, micro-environmental temperature showed a strong negative linear correlation with TCV (R² > 0.8). This study clarified key regulators of CPC micro-environmental convection, offering support for region-specific CPC design optimization and thermal comfort improvement. © 2026 Elsevier Ltd