Experimental study on the seasonal characteristics of occupants' thermal comfort in railway vehicles (Verification of the applicability of PMV/PPD to main line vehicles)

Abstract

The purpose of this study is to clarify the seasonal characteristics of the thermal sensation and comfort of occupants in a main line vehicle in Japan. In addition to the summer and winter experiments conducted in our previous research, we carried out the subjective experiments in the autumn and the spring. The participants rode a main line vehicle stationed at a rolling stock center, and they experienced the non-steady-state thermal environment ranging from around 20℃ to 30℃ and answered questionnaires about their thermal sensation and comfort. Based on the experimental results obtained in the four seasons, the seasonal characteristics of the relationships between the thermal indices called PMV/PPD and the subjective evaluation values were analyzed, and the seasonal differences in the prediction accuracy of PMV/PPD was also examined. The mean thermal sensation has strong correlation with the PMV in all seasons, and the seasonal differences in the relation between them were not found. Furthermore, the percentage of the participants who felt cold/hot sensation in all seasons got good agreement with the PPD. These results support the validity of PMV/PPD as the prediction indices for thermal sensation in railway vehicles. On the other hand, the seasonal differences were found in the relation between the PMV and the percentage of the participants who felt dissatisfied and the relation between the PMV and the percentage of the participants who felt sweaty – in the summer, the percentage of the participants who felt sweaty and dissatisfied was higher than in the other seasons. The root mean square errors of the PPD in the spring, summer, autumn and winter experiments were 12.9pt, 20.4pt, 17.8pt and 11.0pt, respectively. These results suggest, in order to use the PPD as a highly accurate indicator of thermal comfort in Japan all the year around, it should be corrected taking into account the seasonal characteristics of thermal comfort.