[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-108-1-fire-science-016":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-108-1-火災學概要-016","fire-108-1-fire-science-016",108,1,16,"某發生火警的大樓，室內外溫度分別為 800℃與 20℃，中性帶位於 4 樓；6 樓的內外壓差為 60 Pa，若不考慮外部風等其他因素，則 8 樓的內外壓差約為若干 Pa？",{"A":16,"B":17,"C":18,"D":19},"80","100","120","140","C",null,[],false,"本題考點：煙囪效應下,內外壓差與距中性帶高度成正比的線性關係。\n【正解理由】依煙囪效應壓差式 Δp = 3460×(1\u002FTo − 1\u002FTi)×h(Pa),右側除 h 外皆為定值,故不考慮風壓時,各樓層的內外壓差與該層距中性帶的高度成正比。中性帶位於 4 樓,6 樓距中性帶 2 層而壓差 60 Pa,8 樓距 4 層,壓差為其 2 倍即 120 Pa,故選 C。\n【逐項排除】\n(A) 80 Pa 是把壓差為零的基準點誤放在地面,以樓層數比 8\u002F6 乘 60 Pa 求得,忽略零壓差位置是中性帶而非地面。\n(B) 100 Pa 來自誤取每層增量 20 Pa 再往上加兩層(60+20×2),與 6 樓 60 Pa 換算出的每層 30 Pa 實際梯度不符。\n(C) 120 Pa 為正解。每一樓層貢獻 60÷2 = 30 Pa,8 樓距中性帶 4 層,4×30 = 120 Pa。\n(D) 140 Pa 同樣誤用每層 20 Pa 的梯度並累加四層(60+20×4),高估了樓層距離與壓差的換算。\n【演算步驟】Δp 與距中性帶高度 h 成正比;h(6樓)= 6−4 = 2 層,h(8樓)= 8−4 = 4 層;每層壓差 = 60 Pa ÷ 2 層 = 30 Pa\u002F層;Δp(8樓)= 30 Pa\u002F層 × 4 層 = 120 Pa。\n【記憶點】壓差從中性帶起算,距離幾倍壓差就是幾倍。","壓差式的推導可自靜壓開始。室內外空氣柱在高度 h 處的靜壓差為 Δp =(ρo − ρi)×g×h,其中 ρ 為空氣密度、g 為重力加速度。理想氣體在一大氣壓下密度可近似為 ρ ≈ 353\u002FT(kg\u002Fm³,T 為絕對溫度 K),代入後得 Δp = 353×9.81×(1\u002FTo − 1\u002FTi)×h ≈ 3460×(1\u002FTo − 1\u002FTi)×h,這就是常用的煙囪效應係數 3460 的由來,單位為 Pa。\n把本題數據代回可以自我驗算:室外 20℃ = 293 K、室內 800℃ = 1073 K,1\u002F293 − 1\u002F1073 ≈ 0.003413 − 0.000932 = 0.002481,乘以 3460 得每公尺約 8.6 Pa。6 樓要有 60 Pa,對應距中性帶約 7.0 m,恰為兩個樓層(每層約 3.5 m);8 樓距中性帶約 14 m,乘 8.6 得約 120 Pa,與比例法結果一致。這種「用公式回頭驗比例法」的習慣,是避免把基準點放錯位置的最好保險。\n常見單位換算一併記住:1 Pa = 1 N\u002Fm²,10 mmAq(毫米水柱)≈ 98 Pa,1 kgf\u002Fcm² ≈ 98 kPa ≈ 10 m 水頭。一般防火門在兩側壓差超過約 50 Pa 時即明顯難以推開,這也是火場中避難路徑受阻的原因之一。\n延伸考點是逆煙囪效應:當室內溫度低於室外(例如夏季空調場所),Ti > To 的關係反轉,壓差符號隨之相反,氣流改由建築物上部流入、下部流出,煙的擴散路徑整個顛倒。另一個常併考的是中性帶以上為正壓、以下為負壓的分布:排煙口設於中性帶以上才有正壓助排,設於其下反而會把外氣吸入,這一點與本題的線性關係屬同一組觀念。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-108-1-fire-science-015","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？",15,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-108-1-fire-science-017","危害物質可能因混合儲存或載運而衍生危險，則下列那兩類公共危險物品於混合載運時的危險性最低？",17,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-108-1-fire-science-014","依 Thomas 閃燃公式（Thomas Flashover Correlation），有關室內火災發生閃燃所需最小釋熱率，下列敘述何者錯誤？",14,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-108-1-fire-science-018","當氣體進行「壓縮比=2」的斷熱壓縮時，下列對該氣體的敘述何者正確？",18,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-108-1-fire-science-013","比較室內火災閃燃（Flashover）與複燃（Backdraft），下列敘述何者正確？",13,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-108-1-fire-science-019","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？",19,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-111-1-fire-science-016",111,"比較積污導電與金原現象之差異，下列何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-110-1-fire-science-016",110,"市面上販售的 ABC 乾粉滅火器內充填的乾粉滅火藥劑主要成分為：",{"webId":62,"year":63,"stem":64,"number":13},"fire-109-1-fire-science-016",109,"假設建築物外部風速為 10 m\u002Fs，風壓係數為 0.6，空氣密度為 1.0 kg\u002Fm3，其對迎風面建築物所產生的風壓約為？",{"webId":66,"year":67,"stem":68,"number":13},"fire-107-1-fire-science-016",107,"下列何者為海龍替代品滅火藥劑 FE-13 之分子式？",{"webId":70,"year":71,"stem":72,"number":13},"fire-106-1-fire-science-016",106,"下列有關粉塵爆炸之敘述，何者錯誤？",1785123163202]