Development of natural ventilation system that can use low-temperature outdoor air

Abstract Now days, seasonal change in Japan has becoming longer for summer and winter, and shorter for intermediate term such as Spring and Autumn. Therefore, the effective term of natural ventilation has been shorter, which is one of the air conditioning energy saving methods. In order to extend the effective term of natural ventilation, the authors developed a natural ventilation system that can use low-temperature outdoor air. The authors proposed perforated metal duct on ceiling in order to distribute the cool outdoor air evenly in the office room. Officers don’t feel a draft by using a perforated metal duct. Using CFD analysis, the authors compared it with other common natural ventilation systems and confirmed that perforated metal duct is effective. The authors also used ventilation circuit network calculations to consider changes in the panel opening rate to blow air evenly from the ceiling over a depth of approximately 20 meters. Finally, by combining this with the promotion of natural ventilation using exhaust heat from co-generation, the authors achieved stable gravity ventilation. This method can be used not only in Japan but also in warm areas around the world where natural ventilation is possible.