The realization of parallel airflow after flow rectification by the perforated plate under complex inflows

Abstract

The parallel push-pull ventilation system uses uniform, low turbulence, and wide parallel airflow to achieve low diffusion transport of pollutants and reduce the system's energy consumption. Complex inflows caused by local connectors (fans, elbows, and reducers) in front of the air supply device seriously affect the air supply distribution. Currently, most existing studies focus on the performance of parallel push-pull ventilation systems, while lacking theoretical support and parameter guidance to rectify these complex inflows into parallel airflow. This study investigates parallel airflow after rectifying various complex inflows using perforated plates. Within the study context, three typical complex inflows models (fan, elbow, and reducer inflows) are established using dominant numerical and supporting experimental methods. In addition, the rectification effects of inflow velocity, porosity, and hole size of the perforated plate on various complex inflows are compared. The results show that the perforated plate's porosity and hole size should be reasonably matched under different complex inflows to achieve a uniform and low turbulence parallel flow. The perforated plate should have a porosity between 40% and 55% and a dimensionless hole size between 0.014 and 0.031 for elbow and reducer inflows. Swirling flow causes a reduction in the perforated plate's rectification capacity for fan inflow, requiring lower porosity and hole size, while also meaning that the resistance increases significantly. Overall, the study results are anticipated to aid in achieving supply airflow with parallel airflow.