簡易二層之自然補氣口與夾層研究

Abstract

由於一般小居室(面積 200m2)，若堆積可燃物發熱量大，採用「建築物防火避難安全性能驗證技術手冊」進行居室避難安全性能驗證時，有其困難性。故本研究已發展一套適用小居室火災發生時煙層下降預測之簡易二層驗證技術。其數學模式係將空間分為上下兩層，再以質量和能量守衡方程式描述火場熱煙流動形式，透過輸入居室相關條件(如面積、高度、隔間牆材料和排煙方法)及火源大小，即可進行小居室煙流分析。該程式已經過火災模擬軟體FDS和前述驗證技術手冊之模擬結果以及相關實驗數據進行相互比較來驗證其可靠度，結果顯示該程式在適用範圍內，可以相當的能準確預估火場情境。 本研究在該簡易二層程式既有架構上，再予以精進。增加補氣口的設置，考慮由逃生門之排出之煙層質量，以更符合質量守恆之定義，減少煙層於質量流率上的計算誤差；此外亦另加入居室夾層之計算應用，以評估目前常見挑高空間含夾層之居室火災煙流危險度，同時借助FDS 數值模擬軟體進行相關驗證。

If the fire load in a general small room, whose area 200m2, is large enough, then the evaluation of occupancy egress safety as a fire occurs by using the technical manual of building fire-evacuation performance evaluation is very hard to pass authority requirement. Therefore, this research team has been developed a simple two-zone model for smoke layer descending in a room fire. The model divides the room an upper hot layer from a lower cold layer. The mass and energy conservation equations are used to describe the smoke movement in the room fire. The input data include the area, height, partition wall materials and fire load. This predicted results by such model have been justified the corresponding ones obtained from the Fire Dynamics Simulator (FDS) and the technical manual mentioned previously. It also shows the fairly good agreements with the related measurements from the fire experiments. Those indicate that the simple two-zone model for smoke layer descending in a room fire can predict the fire behaviors very well in a suitable space. This study proposes to add air-inlet vent on this two-zone fire model.It considers the mass of smoke layer which exhaust through air-inlet vent into air to better meet the definition of mass conservation. It is also reduces the errors in the calculation of mass fluxes. In addition, the smoke movement in a room with a mezzanine is also taken into consideration in order to evaluate its hazardous degree if a fire occurs in this space. The corresponding simulations by using FDS are also carried out to justify the model.