本論文的研究目的為探討置換式通風對於室內環境流場分層的影響。 研究工作以縮小尺規的壓克力模型進行鹽浴實驗, 模型內部擺置隔板形成兩個相同截面積的相連房間, 根據隔板的開口大小, 實驗組別分為 DCDV(I) 及DCDV(II) 兩個機械置換式通風系列以及對應的兩組自然通風實驗。 浮力源房間於模型頂部供應加入藍色染劑之鹽水, 並在底部開啟一圓孔, 另一相連的供應通風房間則供應不同流量的清水。 此實驗方式中密度升流進行的方向和重力方向相同, 但是與本論文第二章的理論分析模型則為倒置座向的關係。 本論文僅於第二章以理論之座向陳述, 其餘章節皆以實驗的座向說明研究工作的進行與結果。 當置換式通風之供應通風房間與外部環境連接的通風開口封閉並且供應流量小於某特定值時, 通風型式為混合式通風。 在固定浮力源強度的條件下, 當清水供應流量增加, 交界面位置則相對下降。
本研究發現使用置換式通風系統的浮力源房間內入流慣性力與出口的浮力對於室內環境流場分層有重要的影響。 兩種力量的關係以無因次理查遜數來表示, 入流動量的增加會開始擾動原本穩定的分層界面, 並在交界面附近形成混合層, 實驗結果發現浮力和慣性力的比值的對數值與混合層的厚度呈線性關係。

The purpose of this research is to study the stratified flow in a space using displacement ventilation. The salt-bath technique was employed to conduct the experiments and the acrylic reduced-scale model was used to observe the flow patterns. Dye attenuation technique was used to analyze the light intensity data from the recorded images. A partition with an opening was placed in the middle of the rectangular acrylic model to divide the model into two individual chambers. The chamber having a constant buoyancy source is denoted as the forced room, and the other chamber is denoted as the supply room, which supplies fresh water at different flow rates. According to two different connection opening sizes on the partition, the experiments are categorized as DCDV(I) and DCDV(II) two series and the flow pattern in the forced room is investigated. Flow visualization technique is used to observe the flow pattern and the interface level, and the densimeter is used to measure the fluid density. The density plume as a buoyancy source is placed on the ceiling of the forced room and it proceeds in the same direction as that of the gravity force. For thermal plume, the buoyant fluid is ascending and opposite to the proceeding direction of the salt plume in the experiments. But the coordinates of the experiments and the theoretical model are consistent in this study. The results show that the properties of the occupied region in the forced room can be controlled by the volume flow rate of the supply room and the buoyancy
strength in the forced room. Experimental results are in reasonable agreement with the theoretical model. As the supply volume flow rate increases, the distance between the interface level and the source increases and the stability of the stratification becomes weaker. The stratification stability depends on the inertial force of the incoming flow and the buoyancy force of the outgoing flow of the forced room. The results show that the interface stability is disturbed when the inflow supply rate increases. The increase of the inflow inertial force would gradually exceed the buoyancy force to drive the outflow, and a mixing layer is formed between two homogeneous layers.
The thickness of the mixing layer and the logarithm of the ratio of buoyancy force to inertial force have a linear relationship.

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