Developing a physiological-parameter-based thermal sensation model for warm-biased outdoor settings: Step-down phase of the dynamic part

This study develops a thermal sensation model linking subjective thermal sensation votes (TSV) with skin temperature when pedestrians are exposed to a step-down change in thermal status in warm-biased outdoor conditions. 142 human subject tests were completed, with both environmental and physiological parameters collected from 700 subjective-survey conditions, which include skin temperature of 12 body parts, and subjective votes, including TSV, thermal comfort vote (TCV), thermal acceptability (TA), thermal pleasure (TP), and thermal stay willingness (TSW). The prediction of the abdomen, foot, and neck at steady-state has also been updated in this study. Furthermore, a combined sun and wind condition index (SWI) correction term was added to quantify different effects of wind and solar radiation on TSV. Considering natural thermal fluctuations outdoors, highly-dynamic and weakly-dynamic modes were classified and developed based on the derivative of local skin temperature (dT_sk,i/dt). It is found that, among different thermal evaluation scales, TSW exhibited the highest correlations with PET during both the transition and prolonged exposure periods, suggesting it as a more suitable scale for outdoor thermal evaluation. It is perceived that the steady-state model, step-up, and step-down phases of the dynamic model would be integrated to generate both local and overall TSV predictions, and coupled with thermoregulation models to numerically assess thermal conditions of urban spaces during design and planning.