48 / 2025-03-30 10:32:36

A study of the effects of intermittent solar radiation on human thermal comfort and physiological stress responses in passenger cars

passenger vehicle; Intermittent solar radiation; thermal comfort; physiological stress; cortisol

With the increasing production and consumption of automobiles, thermal conditions in passenger cars have drawn increasing attention. The thermal environment inside a vehicle is a crucial factor affecting passenger comfort and overall driving experience. Among various environmental influences, solar radiation is recognized as a primary contributor to heat gain and thermal discomfort. The intensity of solar radiation can fluctuate significantly, leading to rapid changes in the thermal conditions inside the cabin. However, the mechanism behind the effect of high-intensity, high-frequency dynamically varying solar radiation on the dynamic thermal comfort of occupants in passenger cars has not yet been fully clarified. To investigate these issues in greater detail, an experimental study was conducted in which 20 subjects participated. Subjective questionnaires, skin temperature measurements, and saliva samples were collected at three different solar radiation intensities: 200W/m², 400W/m², and 600W/m², respectively. Sudden radiation variations were introduced after 1 minute, 2 minutes, and 3 minutes of exposure to assess their impact. The results demonstrated that at the highest radiation intensity of 600W/m², the skin temperature was the highest, with the frontal skin temperature showing the most significant change, reaching a maximum difference of approximately 1.4℃. Additionally, under the 3-minute exposure condition, the skin temperature increments and decrements were nearly symmetrical with and without radiation variation. Subjective questionnaire responses revealed that 79.6% of participants reported discomfort, particularly in the forehead, left face, and right face. Furthermore, experimental data indicated that solar radiation had a significant impact on cortisol levels, highlighting its physiological effects.