[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-112-1-fire-science-015":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-112-1-火災學概要-015","fire-112-1-fire-science-015",112,1,15,"在煙控系統設計中，兩開口面積均為 1.0 m2，相互串聯後，其等效流動面積為何？（ 2 = 1.414 ）",{"A":16,"B":17,"C":18,"D":19},"0.7 m2","1.0 m2","1.4 m2","2.0 m2","A",null,[],false,"本題考點：煙控分析中多個開口的等效流動面積合成法——串聯開口以「面積平方倒數相加」合成，與並聯開口的「面積直接相加」方向完全相反。\n【正解理由】依孔口流量式 Q＝C·A·√(2ΔP\u002Fρ)，改寫為 ΔP＝ρQ²／(2C²A²)，可見流量固定時壓差與面積平方成反比。串聯路徑上通過每個開口的流量相同、壓差則逐段累加，故合成式為 A(e)＝［1／A₁²＋1／A₂²］^(－1\u002F2)。兩開口各為 1.0 m²，代入得 A(e)＝(1／1²＋1／1²)^(－1\u002F2)＝1／√2＝1／1.414≒0.707 m²，取近似值即 0.7 m²，故選 A。\n【逐項排除】\n(A) 0.7 m² 正是 1／√2＝0.707 m² 的近似值，符合串聯合成式，為本題應選者。\n(B) 1.0 m² 是單一開口的幾何面積，等於忽略第二個開口所增加的流動阻力；串聯後的等效面積必定小於任一個別開口，不可能維持原值。\n(C) 1.4 m² 約為 √2＝1.414，是把 1／√2 取成其倒數，方向相反——串聯只會使等效面積變小，不會變大。\n(D) 2.0 m² 是並聯合成的結果（A(e)＝A₁＋A₂），適用於煙流可各自獨立通過兩個開口的情形，與題設「相互串聯」的條件不符。\n【記憶點】串聯先取平方倒數相加再開根號，結果小於最小開口；並聯直接相加，結果大於最大開口。","等效流動面積（effective flow area）是煙控與滲流計算的基本工具，其推導起點是孔口流量式 Q＝C·A·√(2ΔP\u002Fρ)：C 為流量係數（門縫、窗縫一般取 0.6～0.7），A 為幾何開口面積，ΔP 為開口兩側壓差，ρ 為通過氣體的密度。把式子對 ΔP 求解得 ΔP＝ρQ²／(2C²A²)，壓差與面積平方成反比，這就是串聯合成必須用「平方倒數」的由來：煙氣依序穿過門縫、豎井、風管等路徑時，各段通過的流量相同，而總壓差為各段壓差之和，ΔP(total)＝ΣΔP(i) 直接導出 1／A(e)²＝Σ1／A(i)²。並聯的物理條件相反：各開口共用同一組壓差、流量各自獨立，總流量為分流之和，故 A(e)＝ΣA(i)。\n用電學類比最好記：串聯像電阻串接，導通能力越串越差；並聯像電阻並接，導通能力可以相加。常用數值對照為：兩個相同面積 A 串聯得 0.707A、三個相同面積串聯得 A／√3≒0.577A、n 個相同面積串聯得 A／√n；並聯則為 nA。若一大一小串聯，例如 1.0 m² 與 0.1 m² 串聯，A(e)＝(1／1＋1／0.01)^(－1\u002F2)≒0.0995 m²，幾乎等於小開口本身——串聯路徑由最小開口（瓶頸）主導，這是煙控題常設計的觀念陷阱。\n延伸考點有四類：①同一組合成式用於推估外牆、樓梯間門縫的漏氣面積，再據以估算加壓送風量；②加壓防煙的壓差與門開啟力互為制約，壓差取得過高會使門難以推開，因此漏氣面積估算偏差會直接影響設計成敗；③與煙囪效應（stack effect）併題時，先由中性帶位置判定各層壓差方向，再以等效面積求各層漏煙量；④混合串並聯時，須先把並聯段以直接相加求得分段等效面積，再與其他串聯段做平方倒數合成，兩步順序顛倒即得錯誤答案。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-112-1-fire-science-014","依史蒂芬-波茲曼（Stefan-Boltzmann）公式之定義，輻射熱量與輻射物體絕對溫度的幾次方成正比？",14,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-112-1-fire-science-016","假設空氣中的氧占整體重量的 23%，欲使 1 公斤的丁烷完全燃燒時，需要多少理論空氣量？",16,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-112-1-fire-science-013","依據 Alpert 之天花板噴射流（Ceiling Jet Flow）經驗公式，請問若在 R\u002FH≦0.18 時，該熱氣流溫度與環境溫度之差（△T）和 R 的幾次方成正比？（R：天花板位置與中心軸間的距離，H：天花板距可燃物之距離）",13,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-112-1-fire-science-017","下列那一種爆炸屬於物理性爆炸？",17,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-112-1-fire-science-012","下列何種化合物不是可燃性物質？",12,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-112-1-fire-science-018","若硝化纖維之化學式為 C24H32O12(NO3)8，則其硝化度為多少%？",18,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-015",113,"有關天然氣與液化石油氣之比較，下列敘述何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-111-1-fire-science-015",111,"下列發火源在理化現象歸類上，何者與其他不同類別？",{"webId":62,"year":63,"stem":64,"number":13},"fire-110-1-fire-science-015",110,"下列有關液化天然氣（LNG）與液化石油氣（LPG）之比較，何者正確？",{"webId":66,"year":67,"stem":68,"number":13},"fire-109-1-fire-science-015",109,"下列海龍替代滅火藥劑，何者之化學組成為五氟乙烷？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-015",108,"下列何種現象對於局部電阻所產生的效應恰與其他三者相反？",1785129966501]