本研究探討在具有浮力源(或熱源)的兩並聯房間內由一組機械式抽取設備所驅動之通風模式。兩個房間可以分為浮力源房間(forced room)及抽取房間(extraction room)，其中具有熱源之房間稱為浮力源房間，而另一個具有機械式抽取設備的房間則稱為抽取房間，本研究討論抽取流量對通風流場模式的影響。本論文利用理論分析及實驗室縮尺模型的實驗討論此一問題。在實驗室利用鹽浴法進行通風流場的模擬，以及使用抽水馬達改變抽取流量的大小以觀察流場型式之改變。研究工作的理論分析部分採用點升流理論、虛擬原點修正理論、各孔口的兩側壓差與對應流量的關係以及靜壓方程式，結合上述四種方程式的考量可以推導兩個房間在穩態時的界面層高度(h)以及縮減重力(g′)，在不同抽取流量的條件，另外亦可計算通過各別孔口的體積流率。實驗室的縮尺模型實驗結果與理論模型的估算值相互比較，以瞭解通風流場的重要控制參數與物理機制。本研究發現通風流場的型式取決於抽取流量與臨界流量的關係，當抽取流量小於臨界流量時，流場為小流量模式，抽取房間與外界環境聯結的孔口不會有任何流量，抽取房間與浮力源房間聯結的孔口則完全被鹽水層覆蓋；當抽取流量大於臨界流量時，流場為大流量模式，抽取房間與外界環境聯結的孔口引進外界環境流體，使得清水與模型之抽取房間內的鹽水混合，在抽取房間側，抽取房間與浮力源房間聯結的孔口則完全被清水層覆蓋。本研究結果發現，當抽取房間與浮力源房間聯結的孔口是垂直時，臨界流量則會介於一個範圍，而不像水平的聯結孔口條件只有一個固定的臨界流量值。當鹽水層與清水層之間的界面層高度位於垂直聯結孔口的上、下緣之間時，流場為垂直聯結孔口的轉換模式。實驗結果發現當模型處於小流量模式時，抽取房間不會引進環境流體，因此兩個房間的縮減重力有相當接近的值，縮減重力的數值隨抽取流量的增加而減少，兩個面層界面層的高度則會隨抽取流量的增加而增加；在大流量模式時，抽取房間內的上方孔口開始引進環境流體，因此抽取房間內的縮減重力會小於浮力源房間之縮減重力，抽取房間內的縮減重力則隨著抽取流量的增加而減少，界面層高度則會隨抽取流量增加而增加；浮力源房間的縮減重力值與界面層高度則維持在穩定的數值範圍。

The study explores the flow patterns, which are driven by a mechanical extraction device, in two parallel-connected rooms. The interior space is divided into the forced room and the extraction room. The room with a heat source is denoted as the forced room and the other room, which has a mechanical extraction device, is denoted as the extraction room. This research uses the theoretical analysis and the laboratory scale model to investigate this issue. In the laboratory scale model, the salt-bath technique is used to simulate the ventilation flow patterns, and the pump is used to change the extraction flow rate in order to observe its influence on the flow patterns. In the part of theoretical analysis, the point plume theory, the virtual origin correction theory, the relationship between the flow rate and the pressure difference for each opening and the hydrostatic pressure relationship are used to derive the governing equations of this physical problem. Combining the above equations gives the solutions of the interface level and the reduced gravity in both rooms. This research shows that the flow mode in this problem is determined by the mechanical extraction flow rate, and the geometry of two parallel-connected rooms gives a certain critical flow rate that separates different flow modes. When the extraction flow rate is smaller than the critical flow rate, it is in a small flow rate mode. The extraction exterior opening, which connects the exterior environment and the extraction room, does not have any net flow rate in the small flow rate mode. The internal opening is fully submerged in the brine solution. When the extraction flow rate is larger than the critical flow rate, it is in a large flow rate mode. The opening between the exterior environment

Abstract

and the extraction room starts to introduce the exterior environment fluid, and therefore the fresh exterior water mixes with the brine in the extraction room and the internal opening is submerged by the fresh water. When the internal opening on a vertical partition wall, the critical flow rate is in a range. On the other hand, when the internal opening is on a horizontal partition wall, the critical flow rate is a fixed number. Therefore the location of the interface level distinguishes the modes of the flow. When the internal connection opening is covered by the brine and the fresh water, they are in the small flow rate and the large flow rate respectively. The experimental results show that there is no exterior environmental fluid brought into the extraction room, and the reduced gravity in both rooms has a similar value when the parallel-connected type mechanical ventilation is in the small flow rate mode. Besides the reduced gravity decreases against the extraction flow rate and the interface level increases with the extraction flow rate in the small flow rate mode. In the large flow rate mode, the opening which connected the exterior environment and the extraction room starts to introduce the ambient fluid, and hence the reduced gravity in the extraction room is smaller than that in the forced room. In the large flow rate mode, the reduced gravity in the extraction room decreases against the extraction flow rate, and its interface level increases with the extraction flow rate in the large flow rate mode; the values of the reduced gravity and the interface level in the forced room keep similar.

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