Coupled Analytical Tool of Ventilation Calculation and CFD in Annexation System of Cool/Heat Tube and Natural Ventilation

Natural ventilation airflow rate is generally calculated using indoor and outdoor temperature difference without consideration of heat balance based on the vertical air temperature distribution in simple analytical method. However, room air temperature is influenced by natural ventilation airflow rate, and airflow rate is influenced by room air temperature, so it is necessary to perform a coupled analysis taking into account both heat balance and ventilation to obtain the correct result. Moreover, when there is marked indoor vertical temperature distribution, as found in large enclosures, or when ventilation airflow rate is small, significant computation error will occur if the set value of room air temperature differs greatly from the actual value. To solve two problems mentioned above, the authors developed a natural ventilation tool that takes into account indoor vertical temperature distribution and proposed a coupled simulation method using this tool in conjunction with CFD to simultaneously calculate indoor air flow/temperature distribution and natural ventilation airflow rate. In this paper, the difference between this method and the simple analytical method was shown clearly by comparing calculation results of the two methods about an actual annexation system of cool/heat tube and natural ventilation in a gymnasium.