Thermal sensation model for driver in a passenger car with changing solar radiation

Thermal sensation in cars is different from that in buildings. Transient, asymmetric solar radiation and transient, non-uniform air temperature are the main causes of the difference. This investigation conducted human subject tests with 24 subjects, 62 trials under three outdoor driving conditions. These three driving conditions refers to 1) highly transient environments during the cool-down phases in summer, 2) highly transient environments during the warm-up in winter, and 3) sudden changes in solar radiation in shoulder season. Then the data were used to evaluate the performance of four thermal sensation models: the predicted mean vote model, the dynamic thermal sensation model, a model from the University of California, Berkeley, and a transient outdoor thermal sensation model. The results of the evaluation indicated that none of the models could accurately predict thermal sensation in a car. The sudden change in solar radiation experienced by the driver was identified as an important factor in this discrepancy. Therefore, this study proposed a new thermal sensation model that incorporates the change in the driver's thermal load caused by a sudden change in solar radiation as a predictor. This investigation verified the validity of the new model in a transient and non-uniform vehicular thermal environment.