Effective factors in an optimal design of an air purifier façade to equip the existing buildings’ facades in urban spaces with a high pollution factor, (Case study: Pars Hospital in District 6 of Tehran)

This study aims to design an air purifier façade as a secondary skin façade for the five-story Pars Hospital. The main purpose of this study is to equip the existing buildings’ facades in urban areas with a high percentage of air pollution by an air purifier skin to increase the lifecycle of facades and improve those buildings’ users’ well-being. To choose the case study, three factors were taken into consideration. First, based on the statistics of the air quality monitoring stations, district 6 of Tehran was selected as one of the most polluted and sensitive areas of the city. This is rooted in its central location in the structure of the city, the concentration of administrative, commercial, educational, and recreational zones, as well as the high volume of daily traffic in it. Then, this research focuses on the medical centers and hospitals located in this area and specifically along Keshavarz Boulevard, which is home to many medical centers and hospitals, and from this point of view, it is one of the sensitive and fragile axes in front of air pollution. Eventually, among the medical centers located on this axis, Pars Hospital was selected as the case study due to its specific visitors, patients with respiratory and lung malfunctions, and their priority need for fresh air. Simulation based on computational fluid dynamics (CFD) is used as the research method. In this process, through several stages of simulation and analysis of different parameters with the use of Energy Plus software and Design Builder user interface (v6.1.0.6), an optimal design is presented for a secondary skin, accompanied by a significant increase in air velocity and a decrease in the concentration of pollutants. At simulation time, attention to the studied climate and considering the principles of passive design, are the most important factors in determining the optimal behavior of the building façade, for this purpose in the simulation process, weather information of Tehran city will be used as a database using Energy Plus software with Design Builder user interface.Findings are:1- The optimal distance of the cavity is 150 cm, if the depth of the cavity is less than 150 cm, the cavity of the double-skin façade will benefit more from the stack effect and lead to more heating of the cavity, and if the depth of the cavity is higher than 150 cm, the cavity of the double-skin façade, will not benefit from the stack effect and the temperature of the cavity will decrease, but according to the simulations if the depth of the cavity is considered to be 150 cm, the temperature and size of the cavity will be suitable for growing air pollution absorbing plants and also, the amount of air circulation is done well. 2- For equal distribution of airflow in the cavity, this space should be separated by the floors. 3- Optimal ventilation mode is outside to inside. In this ventilation mode, the purpose is to provide, clean air for breathing, reduce the concentration of pollutants in the cavity, and remove pollutants and polluted air from Pars Hospital. With the increase of fresh air exchange, the concentration of air particles also decreases. 4- The ratio of the area of the air inlet and outlet openings to that of the wall should be 0.075 so that while increasing the speed of the airflow, the age of air in the cavity will be reduced. 5-The optimal form of the secondary skin is grooved in the direction of the wind. With an optimal design of an air purifier skin, the speed of natural airflow in the cavity can be increased and the concentration of pollutants can be reduced. the curved grooves on the facade cause suction and direct the airflow upwards like an air channel, which causes the airflow to continue and increase its speed on the facade. with an optimal design of an air purifier skin, the speed of natural airflow in the cavity can be increased and the concentration of pollutants can be reduced, Research findings in these 5 modes have the most optimal form and function. It should be noted, that the influence of the variables is dependent on others. and all these variables together follow a specific purpose.