Quantitative Evaluation of Effects of Airflow from Cross-flow Fans on Passengers' Thermal Comfort in Commuter Vehicles

Abstract

Almost all commuter trains in Japan are equipped with cross-flow fans in order to circulate the air in a cabin and provide beneficial cooling to passengers, especially during the hot and humid summer seasons. The purpose of this study is to propose a method for predicting the passengers' thermal comfort in non-steady state thermal environments with airflow from cross-flow fans in commuter trains in summer. The proposed method is composed of two calculation parts: a part for calculating sensory temperature based on a human thermoregulation model applicable to non-steady state thermal environments, and a part for calculating the percentage of passengers dissatisfied with the thermal environment based on a statistical model derived from the results of experiments conducted in commuter trains in summer. In order to evaluate the thermal comfort with a cyclic wind from cross-flow fans, the proposed method converts the cyclic wind to a constant wind speed equal to the total amount of heat loss from the whole-body calculated by human thermoregulation model. Applying the proposed method to our previous research where fan-off/fan-on conditions and the congestion rates of below 100%, 120% and 180% had been performed, we examined the prediction accuracy of it. As a result, the mean absolute prediction errors of the proposed method in the congestion rates of below 100%, 120% and 180% under fan-off condition were 9.4pt, 8.2pt and 7.3pt, respectively, and those under fanon condition were 4.5pt, 10.0pt and 13.2pt, respectively.

<b>Evaluation Method of Passenger Thermal Comfort Considering Effects of Airflow by Cross-flow Fan in Commuter Vehicles in Summer</b>

“…Table 2 Information of the experiments [8] Table 3 Examples of subjective evaluation items Table 4 shows the mean absolute error of DyPPD. For the condition with cross-flow fans on, the error tended to be larger for the higher congestion ratio condition.…”

“…This research is based on a method proposed by the authors to evaluate passenger thermal comfort in commuter trains [2] (hereinafter, the proposed method) and investigates the possible application of this method to environments with airflow from cross-flow fans. The prediction accuracy of this method was verified by comparing results from this paper with the results of previous experiments [3,4] whose data were not used to build the proposed method.…”

“…The numerical values correspond to the thermal sensation scale used in the experiment described later (see Table 3 presented later). DyPPDc in (3) and DyPPDh in (4) are indices for predicting the proportion of passengers who feel "cold and dissatisfied" and "hot and dissatisfied" with the in-vehicle thermal environment, respectively. DyPPD, obtained by adding the two in (5), is a predicted value of the thermal dissatisfaction rate that includes both heat and cold causes.…”

“…Fig. 4 Examples of results of the thermal environment measurement and subjective evaluation in the experiment(Condition with the congestion ratio below 100%)[8] …”