複式均勻混合模式於整體換氣之應用

The Application of Multi-cell Well-mixed Model in General Ventilation

均勻混合模式為評估整體換氣室內場所有害物濃度的基本方法，但由於其對有害物於空間中成均勻分佈的假設，致使其在實際應用上受到相當的限制。複式均勻混合模式則可解決上述的限制。複式均勻混合模式基本上係由數個隔間所組成，每個隔間則由一單純均勻混合模式模擬，於是有害物濃度僅於每個隔間而非所有室內環境中成均勻分佈。與單純的均勻混合模式一樣，複式均勻混合模式仍遵循氣流與有害物的守恆關係，而且每一隔間均有各自的守恆關係。本文以此模式為基礎，探討室內氣流形態與整體換氣有害物排除效能的關係，並尋求可達到最有效整體換氣的氣流形態，做為整體換氣設備的設計目標。本文首先探討複式均勻混合模式的建立方式，並以範例說明理論與數值運算方式，再根據複式均勻混合模式的計算結果探討以傳統單純均勻混合模式計算整體平均濃度的適用範圍。經以最適化設計方法分析，求得可達到最大有害物排除效能的置換通風氣流形態。

Traditionally, well-mixed model is a basic way to evaluate the contaminant concentration in an indoor environment. However, the well-mixed model assumes the contaminant concentration distributes uniformly in the indoor environment, which limits applications of the model. In this study, the shortcoming in application is overcome by employing the multi-cell mixing model. Generally, a multi-cell well-mixed model consists of several cells with each cell modeled by an individual simple well-mixed model. The contaminant concentration is assumed to distribute uniformly in each cell instead of in all indoor environment. Similar to a simple well-mixed model, multi-cell well mixed model is established on the conservation of air flow and contaminant with each cell having its own conservation relation. Based on this model, this paper studied the relationship between inter-cell air flow and the capability of the general ventilation to remove the indoor airborne contaminant. The most effective air flow for general displacement ventilation was found and established as a design objective for the general ventilation systems. The way to establish a multi-cell well-mixed model was introduced first. 3 Means to calculate contaminant concentration in each cell analytically and numerically was demonstrated by examples. Validity of the simple well-mixed model was also discussed. Furthermore, the air flow required for the most effective removal of air-borne contaminant was solved by optimization techniques.