[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-108-1-fire-science-011":3},{"subject":4,"subjectSlug":5,"subjectKicker":6,"subjectShort":7,"question":8,"related":27,"sameNumber":52,"hasEssay":26},"火災學概要","fire-science","火災學 · Fire Science","火災學",{"id":9,"webId":10,"year":11,"session":12,"subject":4,"number":13,"stem":14,"options":15,"answer":20,"answerNote":21,"images":22,"imagesPending":23,"lawTimestamp":11,"explanation":24,"explanationDeep":25,"freq":12,"indexable":26},"fire-108-1-火災學概要-011","fire-108-1-fire-science-011",108,1,11,"室內火災所產生的熱煙層由天花板向下沉降的時間直接影響逃生；以此觀點而論，下列何者較不利於逃生？",{"A":16,"B":17,"C":18,"D":19},"較矮的天花板","較大的室內空間","較大的室內樓地板面積","較小的火源周長","A",null,[],false,"本題考點：室內火災熱煙層下降時間的影響因素——由煙量與蓄煙空間的平衡，判斷何種條件對避難最不利。\n【正解理由】熱煙層的下降速率取決於火羽流向上捲吸所產生的煙量，與天花板下方可蓄積煙層的空間體積之比。天花板越矮，一方面上部可蓄煙的體積越小，同一產煙率下煙層厚度增加得越快；另一方面煙層起始高度本來就接近人員頭部，煙層只需下降很短距離即侵入呼吸帶，使可用避難時間大幅縮短，四個選項中對逃生最不利，故選 A。\n【逐項排除】\n(A) 對逃生最不利。天花板矮者蓄煙空間小、煙層起始高度低，煙層迅速壓到呼吸高度，能見度與可用避難時間同時惡化。\n(B) 較大的室內空間代表可蓄積熱煙的體積大，相同產煙率下煙層界面下降較慢，對避難相對有利。\n(C) 較大的樓地板面積使煙層每下降一單位高度所需的煙量增加，界面下降速率變慢，同樣爭取到較多避難時間。\n(D) 較小的火源周長代表火羽流的捲吸周界短、捲入空氣量與產煙率低，煙層生成速度慢，屬有利於避難的條件。\n【記憶點】矮天花板＝蓄煙空間小又離頭近，煙層壓得最快；空間大、面積大、火源小都替避難爭取時間。","煙層下降的物理核心是火羽流捲吸。浮力驅動的火羽流上升過程中不斷把周圍冷空氣捲入，因此越往上、質量流率越大，常用的 Zukoski 型式為 ṁ ≒ 0.071 × Q_c^(1\u002F3) × z^(5\u002F3)，Q_c 為對流熱釋放率、z 為自虛擬火源起算的高度。這條式子解釋了兩件事：一是煙量主要由捲入的空氣構成，燃料本身的質量只佔極小比例；二是捲吸量隨高度以 5\u002F3 次方暴增，天花板越高，同樣的火在到達頂棚前已捲入更多空氣，煙層溫度反而較低、下降較慢，避難條件較佳。火源周長則影響捲吸周界，周長小者捲入量少、產煙率低，同樣延緩煙層下降。\n把煙量換成煙層厚度，就是質量守恆：煙層界面下降速率約等於產煙體積流率除以樓地板面積，故面積越大、下降越慢；而可用的下降行程則取決於天花板高度減去限界煙層高度（避難安全驗證常取人員呼吸高度約 1.8 公尺）。矮天花板同時吃虧在「行程短」與「蓄煙體積小」兩端，這是本題的關鍵。\n工程上以 ASET（可用避難時間）與 RSET（所需避難時間）的比較作為判準，ASET 即煙層降到限界高度、或溫度、輻射熱、一氧化碳濃度、能見度任一項先達到危害基準的時間。對應的改善手段包括設置排煙設備直接抽走煙層、以防煙垂壁與區劃把煙侷限在起火區域、提高天花板高度增加蓄煙容積，以及降低內裝可燃物以壓低熱釋放率。此外天花板高度也會拉長探測器與撒水頭的動作時間，形成雙重不利，是相關考點常見的延伸提問方向。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-108-1-fire-science-010","安裝爆炸氣道（或洩爆孔、氣孔）可適度降低侷限空間中粉塵爆炸的危害，則下列敘述何者錯誤？",10,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-108-1-fire-science-012","建築物之中性帶高度受室內溫度、室外溫度及上下開口的影響，下列敘述何者錯誤？",12,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-108-1-fire-science-009","就同一種可燃性粉塵而言，下列何種措施有助於降低發生粉塵爆炸的危險性？",9,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-108-1-fire-science-013","比較室內火災閃燃（Flashover）與複燃（Backdraft），下列敘述何者正確？",13,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-108-1-fire-science-008","若乙烷的燃燒熱為 350 kcal\u002Fmole，依據 Burgess-Wheeler 法則，下列何者最為接近乙烷的燃燒下限？",8,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-108-1-fire-science-014","依 Thomas 閃燃公式（Thomas Flashover Correlation），有關室內火災發生閃燃所需最小釋熱率，下列敘述何者錯誤？",14,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-011",111,"下列何者非為影響閃燃的因素？",{"webId":58,"year":59,"stem":60,"number":13},"fire-110-1-fire-science-011",110,"輻射熱是造成木造建築物延燒原因之一，下列何者正確？",{"webId":62,"year":63,"stem":64,"number":13},"fire-109-1-fire-science-011",109,"某一線徑 2.0 m\u002Fm 之電線 1 km 長之電阻值為 5.657 Ω，熱阻抗為 378。若周遭溫度為 20℃，當此 10 cm 長之電線通過 10 安培時，其芯線溫度（℃）約為多少？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-011",107,"在高科技無塵室作業中，下列敘述何者不是避免人員帶靜電產生危害之處理方式？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-011",106,"下列有關擴散火焰的敘述，何者正確？",1785123163139]