[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-106-1-fire-science-024":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-106-1-火災學概要-024","fire-106-1-fire-science-024",106,1,24,"假設正向煙囪效應在中性帶以上 8 m 處的壓差為 10 Pa，若建築物內、外的溫差不變，中性帶以上 20 m 處的壓差為多少？",{"A":16,"B":17,"C":18,"D":19},"15 Pa","20 Pa","25 Pa","30 Pa","C",null,[],false,"本題考點：煙囪效應（stack effect）的壓差計算，重點在壓差與「距中性帶垂直距離」成正比的線性關係。\n【正解理由】依煙囪效應壓差式 ΔP＝3460×(1\u002FT_o－1\u002FT_i)×h，式中 T_o、T_i 分別為室外、室內絕對溫度，h 為量測點與中性帶的垂直距離。題示內外溫差不變，代表括號內那一項為固定值，整式退化成 ΔP＝C×h 的正比關係。由 h＝8 m 時 ΔP＝10 Pa，可得比例常數 C＝10 Pa÷8 m＝1.25 Pa\u002Fm；再代入 h＝20 m，得 ΔP＝1.25 Pa\u002Fm×20 m＝25 Pa，故選 C。\n【逐項排除】\n(A) 15 Pa：把高度差 20－8＝12 m 當成「多出來的一段」再隨手加上 5 Pa，忽略壓差是從中性帶起算的正比量，不是逐段任意累加。\n(B) 20 Pa：直接把高度數值 20 抄成壓差值，混淆了長度單位 m 與壓力單位 Pa，屬於未列式的直覺誤答。\n(C) 25 Pa：由正比關係 10 Pa×(20 m÷8 m)＝25 Pa，與比例常數 1.25 Pa\u002Fm 一致，為正解。\n(D) 30 Pa：誤把倍率取為 3 倍，但 20÷8 實際是 2.5 倍，高估了壓差。\n【記憶點】溫差固定時，離中性帶多遠壓差就多大，高度乘幾倍、壓差就乘幾倍。","煙囪效應的物理根源是浮力：室內空氣受火災或暖氣加熱後密度下降，與室外冷空氣形成密度差，沿垂直豎井（樓梯間、電梯昇降道、管道間）產生由下而上的氣流。壓差通式為 ΔP＝(ρ_o－ρ_i)·g·h，把理想氣體狀態方程 ρ＝P·M\u002F(R·T) 代入並整理，常數項收斂成常見的工程式 ΔP＝3460×(1\u002FT_o－1\u002FT_i)×h（ΔP 單位 Pa、T 用 K、h 用 m）。這個 3460 就是 P·M·g\u002FR 在標準大氣壓下的數值，並非憑空的經驗係數，所以只要溫度條件不變，ΔP 對 h 就是一條過原點的直線，這正是本題只需比例換算的原因。\n中性帶（neutral plane）是室內外靜壓相等的那個高度：其上室內壓力高於室外，煙由室內流向室外並向上竄；其下室外壓力較高，空氣被吸入補充。中性帶越低，上部竄煙的驅動壓差越大，這也是高層建築火災「上層先遭殃」的成因。\n延伸易混淆概念：正向煙囪效應（室內溫度高於室外，冬季或火災時）氣流上升；逆煙囪效應（reverse stack effect，夏季空調建築室內較冷）氣流反而下沉，壓差公式的括號項變號，煙可能被帶往下層。單位換算上，1 Pa＝1 N\u002Fm²，約等於 0.102 mm 水頭；常見加壓防煙的壓差設計值在數十 Pa 量級，與門扇開啟力的限制互相牽制，這也是同一公式常見的另一種考法。\n本考點還常結合排煙與防煙區劃出題：例如問中性帶位置如何隨開口配置移動、問加壓送風如何抵銷煙囪效應壓差、或給定內外溫度直接以 3460 式計算數值。掌握「先判斷哪些量固定、再看剩下的線性關係」的解題順序，這一類題幾乎都能秒解。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-106-1-fire-science-023","燃燒範圍是研判物質物性之重要因素，今有某液化石油氣，其成分為丙烷（C3H8 ）40%燃燒範圍為 2.4%~9.5%、丁烷（C4H10）60%燃燒範圍為 1.8%~8.4%，試求該液化石油氣之燃燒下限為何？",23,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-106-1-fire-science-025","依據實驗，人穿著普通作業服時，其受熱之界限值約為多少？",25,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-106-1-fire-science-022","水的滅火效果，下列何者正確？",22,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-106-1-fire-science-026","有一家用延長線，欲連接電子鍋、熱水瓶及微波爐，耗電功率分別為 550 W、1100 W 及 2200 W，請問該延長線至少應具多大之容許電流？（家用電壓為 110 V）",26,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-106-1-fire-science-021","關於乙炔的性質及火災危險性，下列何者正確？",21,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-106-1-fire-science-027","要使 1 kg 之乙炔完全燃燒，在標準狀態下，其所需之空氣容積為多少？",27,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-024",113,"木材加熱到引火溫度時，可燃性氣體析出量迅速增加，木材的引火溫度約為多少℃？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-024",112,"於空氣中加入氧氣會改變空氣組成，進而影響可燃性氣體的某些燃燒特性，下列何者所受的影響較為明顯？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-024",111,"下列何者非影響建築物中煙霧流動與蔓延的主要因素？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-024",110,"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？",{"webId":70,"year":71,"stem":72,"number":13},"fire-109-1-fire-science-024",109,"在古蹟及歷史建築物火災風險評估指標中，有關防火因應措施安全評估項目中，不包括下列何項？",1785129968072]