Investigation on optimum design of natural ventilation system with solar chimney

In term of energy saving point of view as well as indoor air quality, research on natural ventilation system has become a growing interest for many researchers in recent days. Solar chimney is one kind of passive cooling and ventilating technology that utilizes solar irradiation to generate stack effect, thereby driving natural airflow through the chimney channel. The purpose of this paper is to show principle findings on suitable design of natural ventilation system with solar chimney. The investigation was carried out by CFD simulation validated by field measurement conducted in a four-storey school building located in Fukuoka city, Japan. Results of both CFD simulation and field measurement showed that ventilation rate was greatly influenced by not only the temperature difference of inside chimney and outdoor air, but also by the wind velocity where there was a significant increase of ventilation rate with the two parameters. According to the CFD results, in case of the solar chimney outlet was attached with a hood, the ventilation rate was 12000 [CMH] when the wind direction was parallel to the chimney outlet and 13000 [CMH] when it was perpendicular to the chimney outlet. When the hood was not present, the ventilation rate of 14,000 [CMH] and 8,000 [CMH] were obtained when the wind direction were parallel and perpendicular to the chimney outlet, respectively. From these results, it can be concluded that the presence of hood was very effective and therefore favourable in enhancing natural ventilation of solar chimney regardless of wind direction.