電腦數值模擬在細水霧滅火效能之應用與探討

Abstract

因蒙特婁公約（Montreal Protocol）導致海龍（Halon）滅火系統中止使用，也因此展開替代滅火設備的積極研發。透過廣泛的研究和測試，細水霧系統已經獲得全世界一致認同，可作為在許多應用層面一種有效的取代方案；例如涉及易燃液體的使用、電氣設備、半導體備及戶外的變壓器等。根據 NFPA 750 標準定義細水霧為透過噴頭的洩放，其99%總噴出水之水滴直徑尺寸應小於1000微米（microns）。細水霧系統具備了許多關鍵的抑制機制，包括：熱移除、氧氣取代(置換)、熱輻射阻隔、抑制及滅火。此外，細水霧系統亦有許多方面優於其它滅火系統：如較好的火災抑制能力、煙霧吸附力、較低的水損、無毒、安全及環保。目前在市場上普遍缺乏一個細水霧系統驗證工具，造成細水霧系統在推廣上的困難，而電腦模擬是驗證細水霧系統功能及有效性非常適合的工具。在本論文裡，使用電腦腦模平台來驗證細水霧系統在建築區劃空間及機械空間之應用，由模擬的結果得知，細水霧滅火系統的抑制效能取決於區劃空間內的通風率、火災尺寸、火災類型和噴頭安裝的位置。在模擬期間，細水霧滅火系統在自然通風的狀態下均有效的抑制了火災。然而在強制通風狀態下，由於區劃空間和周圍環境間強大的質傳現象，而導致細水霧滅火系統降低了抑制效能。而透過電腦模擬平台，可以找到細水霧系統在這些區域運用的最佳化的方式。

The phase out of Halon production under the Montreal Protocol has led to constructive research to find a replacement agent for fire protection. Through extensively research and testing, water mist systems have gained worldwide acceptance as an effective solution in many applications, such as those that involve flammable liquids, electrical equipment, semiconductor facilities, and outdoor transformers. The NFPA 750 standard defines “water mist” as a water spray discharged through a nozzle in which 99% of the water spray’s volume comprises water particles less than 1,000 microns in diameter. A water mist system combines the key suppression mechanisms of heat extraction, oxygen displacement and radiant heat blocking, suppress and extinguish fires. In addition, water mist systems provide the following advantages over other suppression systems: superior fire suppression, smoke absorption capability, minimal water damage, non-toxicity, non-asphyxiating, and environmentally friendly. The absence of water mist system verification tool presents a major obstacle to promoting water mist technology in the market. Computer modeling is a suitable tool to verify the effectiveness and performance of water mist systems. The simulations results show that water mist suppression effectiveness is dependent on the ventilation rates, fire size and type, location in the compartment and characteristics of the water mist system used. During simulations, the water mist system effectively extinguishes fires under natural ventilation. Under forced ventilation, however, water mist fire suppression effectiveness is substantially reduced due to the strong mass exchange between the compartment space and its surroundings. Also using computer modeling platform verifies the water mist system used in compartment space and machinery space that can be also found the way to optimize water mist system in these application areas.