Planning of ventilation for a large parking space by using temperature difference

We designed a roofed parking lot for a large wholesale market in Sapporo City to protect trucks and cars from snow and rain. Every day, the area attracts a large number of vehicles including trucks. Drivers often leave the engines running for heating in winter and cooling in summer. Exhaust gases poison the air, creating a serious environmental problem. The roof of the new parking lot is equipped with two kinds of chimneys, such as high chimneys to exhaust waste air and low chimneys to supply fresh air. We evaluated the effectiveness of the chimneys by using a specially designed model and CFD to observe the airflow. However, every high chimney didnt work for exhausting waste air. In the model, the amount of air under the roof gathered in the center and the concentration of gas in that area were higher than in other areas. If the inner surfaces of the high chimneys are painted dark and illuminations are installed in them, the chimneys can exhaust waste air quite effectively in the daytime, particularly in the morning when outdoor temperatures are low. Such effects were observed by CFD.