Numerical analysis on a solar chimney with an inverted U-type cooling tower to mitigate urban air pollution

The acceleration of urbanization process, which triggered a series of environmental issues, has become increasingly prominent. Air pollution, especially atmospheric fine particulate matter (PM2.5), is one of the most severe pollutions affecting the human health and living standard. In this article, a novel solar chimney with an inverted U-type cooling tower and a water spraying system (SCIUCTWSS) was proposed to mitigate the urban air pollution. In this system, an inverted U-type cooling tower was used to take place of the traditional chimney erected in the center of the collector; a water spraying system was installed at the turning point of the inverted U-type cooling tower to enhance the driving force; a filtration screen is placed near the entrance of the collector to filter out PM2.5 and large particulate matter from the airflow. The clean air out of the system's outlet can immediately improve the air quality in the spectrum of human activity. A mathematical model to describe the fluid flow, heat transfer of the system was further developed. Influence of injected water from the water spraying system on the pressure, velocity, temperature, and air density distributions were analyzed. The numerical simulation results indicated that water injection is efficient that can strengthen the natural convection and has a positive influence on the heat transfer process within the system. This proposed SCIUCTWSS in this article is able to process atmospheric air at a volume flow rate of 810 m3/s, corresponding to the volume of 69,984,000 m3 of air to be cleaned in one day. However, in view of the economic and human comfort, the amount of injected water should be taken into comprehensive consideration.