通勤電車、ドア開閉で換気効果　山手線想定、富岳で―理研など

　理化学研究所は２６日、スーパーコンピューター「富岳」（神戸市）を使った計算で、駅間が短く頻繁に停車する通勤電車の場合、駅でのドア開閉時の空気の出入りが、窓を開けるのと同等の換気効果をもたらすことが分かったと発表した。
　理研チームリーダーの坪倉誠・神戸大教授らは、通勤電車の先頭車両で定員を超えた混雑時を想定。車内空調による換気が行われ、時速８０キロで走行する条件で、窓を開ける幅や駅に停車してドアを開ける頻度などを変えて空気の流れをシミュレーションし、換気量を計算した。
　窓を大きく開けるほど換気量は増えたが、駅停車時のドア開閉でも勢いよく空気が入れ替わることが判明。２分に１回程度駅に停車し、４５秒間ドアを開ける各駅停車であれば、窓を５センチ開けた列車と同等の換気量を確保できることが分かった。
　坪倉教授は「山手線のように頻繁に停車する電車であれば、ドアの開閉だけで窓開けと同様の効果が得られる。これから寒くなるので、窓を開けるかどうかは停車頻度も考えて判断するといい」と話している。（2020/11/27-07:02）

Calculations by Japan's Fugaku supercomputer have found that opening and closing doors of a local commuter train when it stops at stations brings about the same level of ventilation as from keeping windows of a train open while it is running, government-affiliated research institute Riken said.
   In the research, which was conducted as Japan continues to struggle with the novel coronavirus, a Riken team led by Kobe University professor Makoto Tsubokura calculated the amounts of ventilation in the front cars of commuter trains by simulating the flow of air under various conditions, such as how much windows are open and how frequently doors are opened at stations.
   The team assumed that the trains travel at a speed of 80 kilometers per hour and have air conditioning running for ventilation and that the front cars are overloaded with passengers. While showing that the more open the windows are, the greater the ventilation effect is, the calculations found that the air in the cars is exchanged vigorously through the doors when they are opened and closed at stations.
   If its doors are opened for 45 seconds while at stations, a local train that stops at a station about every two minutes can secure the same amount of ventilation as that for a train with its windows open by 5 centimeters while traveling, according to Riken.
   "For trains that stop very frequently, such as those on the Yamanote Line, you can get as much ventilation effect through opening and closing the doors as through keeping the windows open," Tsubokura said, citing the busy loop line in Tokyo. As it gets colder, how often trains stop at stations can be used as a benchmark to decide whether and to what degree train windows are opened, Tsubokura said.