[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-110-1-fire-science-022":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-110-1-火災學概要-022","fire-110-1-fire-science-022",110,1,22,"火災中所產生的輻射熱量與下列何者成正比？",{"A":16,"B":17,"C":18,"D":19},"輻射物體攝氏溫度的二次方","外界溫差的四次方","輻射物體攝氏溫度的四次方","輻射物體絕對溫度的四次方","D",null,[],false,"本題考點：輻射熱傳的史帝芬–波茲曼定律，關鍵在「絕對溫度」與「四次方」兩個要件同時成立。\n【正解理由】物體表面的輻射熱通量為 E = ε·σ·T⁴,其中 σ 為史帝芬–波茲曼常數 5.67×10⁻⁸ W\u002Fm²·K⁴,ε 為輻射率,T 必須是以克氏(K)表示的絕對溫度。輻射熱量與絕對溫度的四次方成正比，溫度加倍輻射即增為十六倍，這正是火場溫度略為上升、輻射熱卻急遽放大，終而引發閃燃與對面建築物延燒的原因，故選 D。\n【逐項排除】\n(A) 輻射物體攝氏溫度的二次方：溫標與指數兩項皆錯，二次方關係不存在於輻射定律中。\n(B) 外界溫差的四次方：兩表面間的淨輻射為 σ(T₁⁴ − T₂⁴),是「四次方之差」,與「溫差的四次方」在數學上並不相等。\n(C) 輻射物體攝氏溫度的四次方：指數正確但溫標錯誤，攝氏零度並非輻射為零之點，直接以攝氏代入會嚴重低估。\n(D) 輻射物體絕對溫度的四次方：與定律完全相符，正確。\n【記憶點】輻射看 K 不看 ℃,絕對溫度翻一倍，熱量變十六倍。","三種熱傳方式中，傳導與對流大致與溫差成一次方關係，唯獨輻射是四次方，因此在火災成長的中後期，輻射會壓倒性地成為主導機制。理想黑體的輻射率 ε = 1,實際材料介於 0 與 1 之間，燻黑的表面與火焰中的煤煙粒子 ε 相當接近 1,這也是為何濃煙、含碳量高的火焰輻射特別強。\n\n實際計算還須乘上形狀係數(view factor)F,兩物體間的淨輻射為 q\" = F·ε·σ(T₁⁴ − T₂⁴)。形狀係數隨距離增加而快速衰減，近似與距離平方成反比，這是判定建築物間安全距離、以及開口部延燒範圍的理論基礎。\n\n幾個常被一併命題的門檻值：人體皮膚可短時間忍受約 2.5 kW\u002Fm²、木材在有小火源引燃條件下約 12.5 kW\u002Fm² 即可著火、室內地板面接收約 20 kW\u002Fm² 常被當作閃燃發生的判定指標。搭配四次方關係可以理解量級變化：同一表面由 300 K 升到 600 K,輻射熱由約 0.46 kW\u002Fm² 暴增為約 7.3 kW\u002Fm²。\n\n單位換算務必記牢 K = ℃ + 273.15,而溫差在攝氏與克氏是相同的(ΔT 相等),因此傳導、對流計算可直接用攝氏溫差，輻射計算則絕不可以。這一點正是本題 (C) 選項設計的陷阱所在。\n\n就火災階段而言，起火初期以傳導與對流為主，火羽流帶動熱氣層上升並在天花板下累積；當上層熱氣層溫度升至約 500 至 600 ℃,其向下的輻射便足以同時引燃室內其餘可燃物，閃燃於焉發生。四次方關係使這個轉變在極短時間內完成，也是火場風險在成長期後段陡然升高的物理根源。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-110-1-fire-science-021","下列物質在常溫時，何者的熱傳導係數（W\u002Fm∙K）較低？",21,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-110-1-fire-science-023","請問 2 公斤的氫氣（H2）完全燃燒，所需要的理論空氣量為多少公斤？",23,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-110-1-fire-science-020","某室內火場的煙層厚度為 1 公尺，若此時光學密度為 0.173，則該場域中避難反光指標之能見度為多少公尺？",20,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-110-1-fire-science-024","在充足的能量下，下列何種濃度（vol%）的氫氣（H2）為燃燒界限範圍內？",24,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-110-1-fire-science-019","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？",19,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-110-1-fire-science-025","請依據可燃性氣體完全燃燒時的化學理論濃度，計算丙烷的燃燒下限？",25,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-022",113,"一物體在 27℃時輻射出的能量為 E，則當溫度升高到 627℃時輻射出的能量變為多少？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-022",112,"兩種可燃性氣體以等比例混合，其燃燒下限分別為 1.5%、4.5%，則該混合氣體的燃燒下限約為多少%？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-022",111,"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？",{"webId":66,"year":67,"stem":68,"number":13},"fire-109-1-fire-science-022",109,"預防過氧化丁酮之火災爆炸時，下列何種原則正確？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-022",108,"物體在 327℃時的輻射強度為 E，則當溫度升高到 927℃時的輻射強度為何？",1785129967059]