Numerical optimization on newly developed electrostatic enhanced pleated air filters for efficient removal of airborne ultra -fine particles: Towards sustainable urban and built environment

Airborne particulate matters hinder the development of environmentally sustainable cities/towns due to the adverse effects on human health. Because of their small size, ultra-fine particles ( < 100 nm) are believed to exert higher toxicity and cause adverse health effects. For ultra-fine particle removal, widely-used high efficient particulate filter (HEPA) leads to high energy consumption and economic cost. Electrostatic enhanced air filter (EEAF), integrating electrostatic field and fibrous filter, proves to be an efficient and energy-saving tool for fine particle ( > 100 nm) removal. For ultra-fine particles, available experimental research found that filtration efficiency of EEAF was not satisfied ( < 90 %). Thus, the current study adopted numerical method to optimize EEAF by adjusting filtration velocity and electric field in filter. Due to that the traditional Lagrangian-based model failed to predict ultra-fine particles, an Eulerian-based numerical method was used and validated by experiments. For 50 nm particles, efficiency of optimized EEAF was enhanced to 96 %, which was much higher than that of electrostatic precipitator (10 %). The optimized EEAF could save 1/3 of energy consumed by HEPA without sacrificing filtration efficiency. Finally, the coupling design/control strategy of EEAF, urban and indoor environments were analyzed.