Numerical Investigation of Ventilation Design Effects on Exposure Equality in Ventilated Classrooms

Abstract

Schools are crucial buildings, where indoor air quality (IAQ) impacts the academic performance, productivity, and health of students and teachers. Therefore, implementing efficient ventilation systems in high-occupancy areas, particularly classrooms, is essential to prevent accumulation of polluted air and to provide exposure equality among children. This study aims to examine the impact of ventilation design on the spatial pollutant exposure equality in classrooms, specifically focusing on the distribution of submicron particulate matter (PM1) and the air change efficiency. Anthropological data was utilized to accurately represent the geometry of student mannequins, and a three-dimensional classroom model was created accordingly. Steady numerical analyses were conducted parametrically to calculate the air change efficiency for different air flow rates, diffuser angles (diffuser angle: 22 degrees horizontally and 60 degrees and 30 degrees vertically; air flow rate: 3.7 and 8 l/s/person), and PM injection. The three-dimensional airflow and pathogen particle movement in the classroom were determined using realizable k-epsilon turbulence modelling and discrete phase modelling (DPM). For exposure equality, the case with a flow rate of 3.7 l/s/person and a diffuser angle of 60 degrees is the worst design. Front-row students consistently face higher velocity and PM1 concentrations compared to others in all cases, but increasing the flow rate to 8 l/s/person and reducing the diffuser angle to 30 degrees improved the concentration distribution by up to 75%. At a flow rate of 8l/s/person, the decrease in the diffuser angle resulted in a decrease of up to 86% in the velocity values around the heads of these students.