Developing a physiological-parameter-based thermal sensation model for warm-biased outdoor settings: The steady-state part

This study aims to build a thermal sensation model that correlates the subjective thermal sensation votes (TSV) with the body skin temperature in steady-state warm-biased outdoor conditions. The model includes a local TSV model for 11 body parts and an overall TSV model. A total of 86 human subject tests were conducted under varying wind speeds and solar radiation levels using a changeable windbreaker and shading device in real outdoor settings. Data on local and overall TSV, environmental parameters, and physiological responses were collected. Results show a strong correlation between local sweat rate and skin temperature, leading to the selection of local skin temperature as the sole variable for the local TSV model. Individual differences and thermal overshoot outdoors were observed, and a new parameter accounting for the neutral skin temperature variation was introduced into the local TSV model to provide three prediction values, i.e., the mean, the 10th, and 90th percentiles. The overall TSV model, which calculates overall TSV as a weighted average of local TSVs, demonstrated a high fit with actual overall TSV (R² = 0.96). This model is designed to be used with a multi-nodal human thermoregulation model to numerically assess thermal comfort in outdoor spaces.