[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-111-1-fire-science-019":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-019","fire-111-1-fire-science-019",111,1,19,"有關火羽流及天花板噴射流的敘述，下列何者錯誤？",{"A":16,"B":17,"C":18,"D":19},"間歇火焰區上方溫度維持不變","火羽流通常由火焰及熱流組成","火羽流上升遇天花板沿天花板水平移動，形成天花板噴射流","天花板噴射流對地面放射輻射熱，促進可燃物燃燒速度","A",null,[],false,"本題考點：火羽流（fire plume）的分區溫度特性與天花板噴射流（ceiling jet）的形成。\n【正解理由】火羽流自燃燒面向上依序分為持續火焰區、間歇火焰區與浮力羽流區。持續火焰區因始終被火焰包覆，溫度大致維持定值；進入間歇火焰區後火焰時有時無，周圍冷空氣捲吸量增加，溫度隨高度上升而逐漸下降；到浮力羽流區已無火焰，僅剩熱氣流，溫度衰減更快。因此「間歇火焰區上方溫度維持不變」與火羽流的溫度分布不符，故選 A。\n【逐項排除】\n(A) 溫度大致維持不變者為最下方的持續火焰區，間歇火焰區以上因空氣捲吸稀釋而溫度遞減，敘述錯誤，為本題應選者。\n(B) 火羽流由火焰及其上方受浮力驅動的熱氣流共同構成，敘述正確。\n(C) 火羽流上升受天花板阻擋後轉為水平放射狀擴散，即形成天花板噴射流，敘述正確。\n(D) 天花板噴射流與其下方熱煙層對地面放射輻射熱，加速可燃物熱分解與燃燒，敘述正確。\n【記憶點】火羽流三區只有最下面的持續火焰區溫度不變，往上一路遞減。","火羽流是室內火災熱傳與探測理論的起點。燃燒面上方的高溫氣體因密度較低而受浮力驅動上升，上升過程中不斷把周圍冷空氣捲吸進來，這個捲吸量隨高度增加而增加，因此質量流率愈上愈大、溫度愈上愈低。依火焰的存在型態可分三區：最下方的持續火焰區火焰恆定存在，溫度大致維持在定值；中段的間歇火焰區火焰時而出現時而斷續，平均溫度開始下降；最上方的浮力羽流區已無火焰，中心線溫度升高值隨高度呈負三分之五次方的關係衰減，速度亦同步下降。這也解釋了為什麼同一場火災，天花板愈高、熱煙抵達天花板時的溫度愈低，探測器與撒水頭的動作也愈慢。\n火羽流受天花板阻擋後轉為水平流動，形成厚度僅為天花板高度百分之十上下的天花板噴射流，最高溫度出現在貼近天花板下方一小段距離處。探測器與撒水頭之所以設在天花板面下方，正是為了讓感熱、感煙元件落在這層高溫高速的流層之內；設在梁下深處或距天花板過遠，都會使動作時間延後。天花板噴射流的溫度與速度隨著離火源水平距離增加而衰減，這也是探測器有效範圍與裝置間距設計的理論來源。\n易混淆概念可對照記憶：火羽流是垂直、由浮力驅動；天花板噴射流是水平、由撞擊後的動量與浮力共同驅動；熱煙層則是熱煙在天花板下方累積後形成的靜態分層。三者依序發生，最後熱煙層向下放射輻射熱，回饋加熱地面可燃物，構成閃燃的前置條件。延伸考點包括火焰高度與熱釋放率的關係、捲吸對煙量估算與排煙量計算的影響，以及天花板高度對探測器動作時間的影響。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-111-1-fire-science-018","下列何者非電線走火之原因？",18,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-111-1-fire-science-020","下列對於燃燒要素的敘述，何者錯誤？",20,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-111-1-fire-science-017","有關閃燃（Flashover）與複燃（Backdraft）的敘述，何者錯誤？",17,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-111-1-fire-science-021","下列有關熱量傳遞的敘述，何者正確？",21,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-111-1-fire-science-016","比較積污導電與金原現象之差異，下列何者錯誤？",16,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-111-1-fire-science-022","連棟式木造建築物引發火災，消防隊射水同時拆除未受火勢波及的房屋，請問其採取的滅火方法係下列何者？",22,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-110-1-fire-science-019",110,"當發生危害物質災害時，為降低對民眾及搶救人員的危害，應迅速劃定管制區域，下列區域何者一般以黃色標示？",{"webId":58,"year":59,"stem":60,"number":13},"fire-109-1-fire-science-019",109,"若一物體的溫度為 327℃，輻射率（ Emissivity）為 0.1，已知史蒂芬–波茲曼常數為 5.67×10-8 W\u002Fm2k4，則其輻射強度（Emissive Power）約為多少？",{"webId":62,"year":63,"stem":64,"number":13},"fire-108-1-fire-science-019",108,"下列何種滅火劑使用於金屬火災時，沒有「與金屬產生化學反應而衍生危害物質」的可能？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-019",107,"電線因火災燒熔而短路所形成之熔珠，稱為下列何者？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-019",106,"研究火災特性時，所謂的「火載量」（Fire Load）是指：",1785123161995]