基於計算流體力學評估教室內不同換氣型態對氣膠分布與傳播之影響-以台北某大學教室為例

Abstract

良好的通風換氣系統對於有效地稀釋與去除潛在有害氣膠扮演了至關重要的角色，進而降低封閉環境內病毒傳播之風險。本研究利用計算流體力學（CFD）模擬台北市某大學階梯教室內之穩態流場，旨在評估不同換氣模式、流量、教室佔用人數對流場結構以及氣膠傳播之影響。本研究基於現有教室之前方抽氣模式(Model 1)，欲比較其與天花板進氣抽氣模式(Model 2)在不同條件下之流場結構以及對氣膠分布之影響。研究結果發現，適中的流量對於有效排除微粒方面最為理想，過高的流量反而會導致湍急和不均勻的氣流模式，除了降低通風效率，也可能對室內的舒適度造成影響。此外，我們發現兩模型在教室滿員情境下之微粒排除率皆比教室梅花座情境下還要高，人員本身對氣流的阻力和引導作用可能是造成這一現象的主要原因之一，教室滿員情境下，人員形成的阻力使得氣流被迫繞行，增加氣流的混合度，較大程度减少死角的形成；而梅花座情境下，氣流較能夠自由地穿梭空位區域，進而形成更大型的迴流區。本研究發現教室滿員情境下，Model 2在四種流量之微粒排除率均高於Model 1，且根據微粒最終流布結果發現，Model 1呼出之微粒隨氣流朝教室前方擴散，微粒從抽氣口排出之前，多數會經過座位區；而Model 2因抽氣口在天花板，呼出微粒較容易直接被往上吸，減少微粒在教室內的傳播範圍，這表明Model 2在控制氣膠傳播方面更為有效。

Effective ventilation is crucial for diluting and removing harmful aerosols, reducing virus transmission risk in enclosed spaces. Computational Fluid Dynamics (CFD) was used to simulate the steady-state flow field in a lecture hall at a university in Taipei, evaluating the impact of different ventilation modes, flow rates, and occupancy levels on flow field structure and aerosol transmission. This study compares the existing front exhaust mode (Model 1) with a ceiling exhaust mode (Model 2) under various conditions. The results indicate that moderate flow rates are most effective for particle removal, as high flow rates can cause turbulent, uneven airflow, reducing ventilation efficiency and indoor comfort. In the fully occupied scenario, the particle removal rate is higher than in the checkerboard seating scenario. This was likely because the personnel themselves create resistance and guide the airflow, forcing it to circulate more thoroughly and reducing the formation of dead zones. In a checkerboard seating scenario, airflow moves more freely through empty spaces, leading to larger recirculation zones. We also found that Model 2 represented a higher particle removal rate across all flow rates compared to Model 1. In Model 1, exhaled particles spread toward the front before being expelled, often passing through the seating area. In Model 2, particles were more easily drawn upward and out, reducing spread within the classroom. This indicates that Model 2 was more effective in controlling aerosol transmission.