Exploring the correlation and synchronicity between environmental factors and occupant thermal response in dynamic outdoor cabin environments

Abstract

To improve the cabin thermal environment and explore advanced automotive air-conditioning control methods, it is essential to understand the key factors affecting occupant thermal response as well as the synchronicity of the thermal response to environmental changes in outdoor conditions. Given the current gaps in research, this study conducted outdoor experiments in summer to analyze the correlation and synchronicity between the cabin thermal environment and occupant thermal sensation as well as facial skin temperature. Results showed that, during the cooling phases of experiments with high initial cabin air temperatures, occupant thermal sensation improved significantly within 7 min. After 15 min, facial skin temperature and thermal sensation reached quasi-steady states. Thermal sensation was primarily influenced by air temperature, followed by solar radiation, and exhibited significant synchronicity with changes in these factors. When the air temperature stabilized at around 26 °C, every 200 W/m2 of solar radiation exposure increased the thermal sensation unit during the 40-min experiment period. Cheek and nose skin temperatures were significantly correlated with air temperature and solar radiation, and were sensitive to environmental changes, synchronizing with changes in air temperature and relative humidity. Further analysis showed the feasibility of using cheek and nose skin temperatures to characterize the occupant thermal sensation in a cabin. Additionally, this study found sex differences in the occupant thermal response in a cabin. The results provide insight into the key optimization parameters for comfort-oriented cabin thermal environment design and offer support for future air conditioning control in cabins based on thermal imaging.