A novel complex air supply model for indoor air quality control via the occupant micro-environment demand ventilation

Protection of indoor air quality and human health can be achieved via ventilation, which has becomes one of the most important tasks for sustainable buildings. This approach also requires highly efficient and energy saving methods for modern building ventilations consisting of a set of parameters of the complex indoor system. Therefore, the advancement in understanding the characteristics of various ventilation methods is highly necessary. This study presents one novel air supply model for the complex occupant micro-environment demand control ventilations, to analyze the efficiency of various ventilation types. This model is established primarily according to the momentum and mass conservations, and goal of occupant micro-environment demand, which is a complex system with the characteristics of diversity and dynamic variation. As for different occupant densities, characteristics of outdoor air supply for controlling gaseous pollutant and three basic features of outdoor airflow supply reaching occupant micro-environment were obtained. This research shows that for various types of occupant density and storey height, the rising and descending rates of the demand outdoor airflow in mixing ventilation are higher than those under displacement ventilation conditions. In addition, since the structure is better designed and sewage flow is more efficient, the mixing ventilation also requires a much higher peak demand outdoor airflow than its counterpart. The increase of storey height will lead to a decline of pollutants in the breathing zone and the demand outdoor airflow. Fluctuations of air flow diffusion caused by the change of occupant density in architectural space, will lead to variations of outdoor airflow reaching occupant micro-environment. Accordingly, it would lead to the different peak values of demand outdoor airflow, and the difference becomes even significant if the occupant density increases. The variations of the air supply and fraction of air reaching the occupant-breathing zone show the characteristics of a complex system. This research is meaningful for design and optimization of the complex indoor air environment in sustainable buildings.