jismart2024064: Numerical Investigation of Optimizing Spray System Operating Parameters to Improve Urban Summer Thermal Environment

Abstract

Urbanization has resulted in distinct environmental challenges, including urban heat islands. The phenomenon of urban heat islands serves to exacerbate global warming, increase the incidence of heat-related mortality and render climate patterns more unpredictable. Traditional passive evaporative cooling has low cooling efficiency and limited application scenarios. The spray system utilizes injected droplets to rapidly absorb heat from the surrounding air, providing cooling and effectively improving the local hot and humid microenvironment in urban areas during the summer. However, the complexity and diversity of spray system operating parameters make optimizing cooling effects difficult in practice. To address these challenges, this study used a computational fluid dynamics (CFD) model and validated a spray evaporation cooling model for hollow cone nozzles based on experimental data from a wind tunnel. The study investigated the effect of spray system operating parameters on cooling efficiency. The outdoor meteorological parameters of Qingdao were selected as boundary conditions to study the effects of droplet temperature, droplet velocity, mean droplet diameter and nozzle cone angle parameters on the cooling effect in the area. A systematic parametric analysis of these parameters was performed. The study shows that the spray system can improve the summer thermal environment in high temperature and high humidity areas, and the optimization of the parameters can further improve the cooling effect. The droplet temperature, droplet velocity, mean droplet diameter and nozzle angle reduced the outdoor temperature by 6.18°C, 3.91°C, 4.8°C and 4.05°C, respectively. And the relative humidity was increased by 25%, 15%, 18% and 16%, respectively. In addition, varying droplet velocity and droplet mean diameter were effective in increasing droplet evaporation efficiency and thus reducing temperature.