[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-111-1-fire-science-012":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-111-1-火災學概要-012","fire-111-1-fire-science-012",111,1,12,"密閉空間燃燒中天花板會向地面放射大量輻射熱促進地面可燃物燃燒速度，此現象為何？",{"A":16,"B":17,"C":18,"D":19},"熱傳導回饋","熱輻射回饋","熱對流回饋","閃燃效應","B",null,[],false,"本題考點：室內火災中天花板與熱煙層對地面可燃物的熱回饋機制，考的是三種熱傳方式的辨識。\n【正解理由】熱由高溫面以電磁波形式越過空氣直接傳給遠處物體、不需介質接觸者為輻射。密閉空間燃燒時，天花板及其下方蓄積的高溫熱煙層形成大面積高溫輻射面，向下方地面持續放射輻射熱，使地面可燃物受熱分解加速、燃燒速度提高，此即熱輻射回饋（radiation feedback），也是閃燃得以成立的主要熱源，故選 B。\n【逐項排除】\n(A) 熱傳導須靠固體分子振動逐層傳遞，必須有直接接觸的介質路徑；天花板與地面可燃物之間隔著空氣，不符傳導的成立條件。\n(B) 天花板與熱煙層以電磁波向下方放射熱能，符合輻射的定義，作用對象為地面全部可燃物，與題幹敘述完全相符，為本題應選者。\n(C) 熱對流靠流體本身流動攜帶熱量，火場中熱氣流受浮力向上竄升並沿天花板水平擴散，方向與「向地面放射」不合。\n(D) 閃燃是輻射回饋累積到門檻後、地面可燃物幾乎同時起火的結果現象，題幹敘述的是造成閃燃的機制本身，而非閃燃本身。\n【記憶點】天花板「往下烤」是輻射回饋，往上竄、橫向流的才是對流。","熱傳的三種方式在火災學上各有辨識關鍵：傳導看有無接觸與材料的熱傳導係數，對流看流體本身是否流動攜熱，輻射則看溫度與角係數，且不需要任何介質，真空中照樣成立。輻射熱的強度由史蒂芬-波茲曼定律描述，放射能量與放射面絕對溫度的四次方成正比，因此熱煙層溫度由攝氏三百度升到六百度時，絕對溫度僅增加約一點五倍，輻射熱卻暴增為原來的五倍以上。這說明為什麼室內火災在成長期後段，主導的熱傳方式會由對流轉為輻射：熱煙層一旦增厚、增溫，它就成為一面覆蓋整個房間的高溫發熱板。\n熱輻射回饋也解釋了區劃空間與開放空間燃燒行為的差異。同一堆可燃物在戶外燃燒時，只有火焰自身的輻射回到燃料表面；在室內則多了天花板、熱煙層與被加熱的牆面三個輻射來源，燃燒速度可以數倍於戶外，這是室內火災成長遠比想像中快的物理原因，也是閃燃能夠成立的前提。當地面接受的輻射熱通量累積到約每平方公尺二十千瓦時，一般木質可燃物的表面即可被引燃，室內遂進入全面燃燒。\n易混淆對照可以這樣記：貫穿樓地板的金屬管路把熱帶到隔壁房間是傳導；熱煙沿走廊擴散、循垂直管道間上竄形成煙囪效應是對流；隔著防火間隔把鄰棟外牆烤到起火、天花板把地面可燃物烤到起火，則都是輻射。輻射熱的傳遞量除了溫度以外，還取決於放射面與受熱面之間的角係數，也就是兩者相對的面積、距離與夾角；天花板之所以是最有效率的回饋面，正因為它面積大、正對地面、角係數接近最大值，這也是密閉空間比開放空間更易蓄熱的幾何原因。延伸考點包括輻射熱隨距離平方反比衰減所導出的防火間隔計算、火羽流上升受阻後形成的天花板噴射流，以及水霧滅火設備藉水滴遮斷輻射熱的作用原理。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-111-1-fire-science-011","下列何者非為影響閃燃的因素？",11,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-111-1-fire-science-013","高層建築物火災特性下列何者錯誤？",13,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-111-1-fire-science-010","火場當中煙毒危害，下列敘述何者錯誤？",10,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-111-1-fire-science-014","普通木造建築物旁欲蓋 9 公尺高之建築物，其延燒係數為 3 級（係數為 0.15），其防火間隔應保持多少公尺？",14,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-111-1-fire-science-009","有關粉塵爆炸的敘述，下列何者錯誤？",9,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-111-1-fire-science-015","下列發火源在理化現象歸類上，何者與其他不同類別？",15,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-110-1-fire-science-012",110,"根據 NFPA265 對閃燃現象（flashover）之定義，下列敘述何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-109-1-fire-science-012",109,"下列常見之乾粉滅火藥劑敘述何者正確？",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-012",108,"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？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-012",107,"下列何者並非容易悶燒材料之特性？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-012",106,"凡不能與氧化合之物質均非可燃物，例如氦（He）、氖（Ne）、氬（Ar）等氣體。但氮（N2）可與氧化合，亦被視為非可燃物，是因為其反應過程具何因素？",1785123161927]