[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-107-1-fire-science-030":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-107-1-火災學概要-030","fire-107-1-fire-science-030",107,1,30,"固體燃料火焰延燒最快的方式為下列何者？",{"A":16,"B":17,"C":18,"D":19},"向上","向下","水平","與延燒方向無關","A",null,[],false,"本題考點：固體可燃物的火焰延燒方向性，考的是火焰傳播方向與預熱區的相對關係。\n【正解理由】火焰是高溫低密度氣體，浮力使火焰與熱煙持續往上竄，上方尚未燃燒的材料同時承受火羽流的對流加熱與火焰的輻射加熱，預熱最充分、表面最早裂解出可燃氣體並達到燃燒下限，因此火焰陣面沿表面向上推進最快，屬於同向流火焰傳播；向下與水平則為逆向流傳播，火焰被浮力帶離未燃面，只剩有限的輻射與固體傳導可供預熱，速度低上一至數個數量級，故選 A。\n【逐項排除】\n(A) 正確：向上延燒兼具對流與輻射預熱，又有煙囪效應助長，是最快的方向，理由如上。\n(B) 錯誤：向下延燒時火焰往上離開未燃區，預熱最弱，是三個方向中最慢者，實驗上常僅為每分鐘公釐等級。\n(C) 錯誤：水平延燒時火焰僅部分貼附材料表面，預熱效果介於向上與向下之間，並非最快。\n(D) 錯誤：延燒速度受浮力與預熱條件支配，方向性極為明顯，不可能與方向無關。\n【記憶點】火往上跑最快——上竄有對流加輻射，向下只剩輻射，快慢差好幾個數量級。","火焰傳播依火焰流動方向與傳播方向的相對關係分為兩型：同向流傳播(火焰與傳播方向一致，如向上延燒)與逆向流傳播(火焰逆著傳播方向，如向下與水平延燒)。決定速度的關鍵是預熱區長度——火焰把未燃表面加熱到熱分解溫度所影響的距離。向上延燒時，火羽流貼著壁面上竄，預熱區可長達數十公分甚至數公尺，且隨火焰變高而加速，呈現自我加速的正回饋；向下延燒的預熱區只有數公釐，幾乎完全靠輻射與固體內部傳導，速度因此穩定而緩慢。實驗上厚質壓克力板向下延燒約每分鐘公釐等級，垂直向上延燒卻可達每秒數公分以上，差距輕易超過兩個數量級。\n把材料傾斜也會改變速度：傾角愈接近垂直向上，火焰愈貼附表面，延燒愈快；向下傾斜則火焰離開表面，速度下降。這解釋了幾個經典火場現象——建築外牆保溫材與帷幕牆的立面延燒為何一發不可收拾、垂直電纜束為何比水平電纜架延燒更快、窗口噴出火焰為何會沿外牆向上層竄燒形成上下層延燒。\n對照記憶：向上延燒受對流主導，向下與水平延燒受輻射主導；通風、材料厚度、熱慣性(密度乘比熱乘熱傳導係數)則共同影響絕對速度，薄材料因熱慣性小而比厚材料更快被點燃。\n幾何配置也會放大方向效應：兩片可燃面相互平行且間距狹窄時，彼此的輻射會互相回饋，使夾縫內的溫度遠高於單面燃燒，堆疊紙箱、貨架走道與書櫃間隙的火勢因而特別猛烈；若這個狹縫又是垂直的，便同時具備輻射回饋與煙囪效應，延燒速度可再往上跳一級。\n延伸考點：同一組概念會以「火焰傳播速度的影響因素」「外牆立面火災」「電纜火災」「森林火災上坡延燒為何較快」等形式出題，上坡延燒之所以快，原理與向上延燒完全相同，都是火焰貼近未燃燃料造成的預熱強化。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-107-1-fire-science-029","下列何者並非學校實驗室火災之特性？",29,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-107-1-fire-science-031","下列何者並非造成電氣火災的原因？",31,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-107-1-fire-science-028","下列何者並非古蹟火災防護之特性？",28,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-107-1-fire-science-032","下列何者並非防火區劃構件構造之性質？",32,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-107-1-fire-science-027","下列何者並非高科技廠房火災之特性？",27,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-107-1-fire-science-033","燃燒時若生成的熱與散失的熱保持平衡，燃燒溫度保持均勻之燃燒為下列何者？",33,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-030",113,"有關煙控分析中「等效流動面積」的定義，下列敘述何者正確？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-030",112,"滅火藥劑的供給率關乎火災初期的滅火成敗、滅火時間與藥劑使用量，下列敘述何者錯誤？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-030",111,"下列對高樓逃生通道設計原則的描述，何者錯誤？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-030",110,"某建築物火場產生大量煙霧，正向煙囪效應在中性帶以上 10 公尺處的壓力差為 12 Pa，若建築物內、外的溫度差不變，請問中性帶以上 20 公尺處的壓力差為何？",{"webId":70,"year":71,"stem":72,"number":13},"fire-109-1-fire-science-030",109,"海龍替代滅火藥劑中，下列何者在大氣之滯留時間最久？",1785129967875]