[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-108-1-fire-science-014":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-014","fire-108-1-fire-science-014",108,1,14,"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？",{"A":16,"B":17,"C":18,"D":19},"隨室內火載量增加而提高","隨室內空間增加而提高","隨對外開口面積增加而提高","隨對外開口高度增加而提高","A",null,[],false,"本題考點：Thomas 閃燃公式的變數組成，判斷哪一項不會影響閃燃所需的最小釋熱率。\n【正解理由】Thomas 半經驗式為 Q = 7.8A_T + 378A_o√H_o,Q 為觸發閃燃所需最小釋熱率(kW),A_T 為扣除開口後的室內總內表面積(m²),A_o 為開口面積(m²),H_o 為開口高度(m)。式中只有內表面積與開口幾何兩組變數，並不含火載量；火載量決定火災能燒多久與最盛期的溫度，不決定觸發閃燃的臨界釋熱率。選項敘述與公式不符，故選 A。\n【逐項排除】\n(A) 敘述錯誤，為本題應選者。公式中沒有火載量項，火載量增加並不會提高閃燃所需的最小釋熱率。\n(B) 敘述正確。室內空間變大使總內表面積 A_T 增加,7.8A_T 項變大，牆面與天花板吸走的熱更多，需要更大釋熱率才能達到閃燃。\n(C) 敘述正確。開口面積 A_o 增加使 378A_o√H_o 項變大，經開口流失的熱氣量增加，閃燃所需釋熱率隨之提高。\n(D) 敘述正確。開口高度 H_o 以平方根形式進入同一項,H_o 增加使通風因子變大、排熱增強，所需釋熱率亦提高。\n【記憶點】Thomas 式只看內表面積與通風因子，火載量不入列。","這條式子不是憑空給的，而是室內熱平衡的簡化。火源釋出的熱在閃燃前主要走三條路：經開口隨熱氣流帶走、傳入牆面與天花板等圍壁蓄積、以輻射與對流回饋給室內可燃物。要維持上層熱氣層達到閃燃溫度，火源釋熱率必須同時補足前兩項損失，於是形成兩個加項:7.8A_T 對應圍壁的熱損失，係數帶有壁面傳導特性的經驗值;378A_o√H_o 對應開口的熱氣流失。\n通風因子 A_o√H_o 的由來值得記牢。開口進出氣的流速由浮力壓差決定，依柏努利關係流速正比於高度差的平方根，故流量正比於開口面積乘以開口高度的平方根，寫成 A_o√H_o(單位 m^5\u002F2)。這個因子在火災學裡到處出現：最盛期的燃燒速率 m ≈ 0.09A_o√H_o(kg\u002Fs)、通風控制與燃料控制的判別，都靠它。\n單位與量級也常入題。以一間 4m×5m×3m、開口 2m 寬 2m 高的房間為例，總內表面積約 94 m²(已扣除 4 m² 開口),A_o√H_o = 4×√2 ≈ 5.66,代入得 Q ≈ 7.8×94 + 378×5.66 ≈ 733 + 2140 ≈ 2873 kW,約 2.9 MW,與一般住宅房間閃燃需 1 至 3 MW 的經驗值相符，可用來檢查記憶是否走樣。\n易混淆對照是 MQH(McCaffrey-Quintiere-Harkleroad)上層溫升關聯式，它推估的是上層熱氣層的溫升值，輸入同樣包含通風因子與圍壁熱慣量;Thomas 式則直接給出閃燃門檻的釋熱率。兩者常被併考，判別關鍵在於問的是溫度還是釋熱率。火載量則屬於另一組考點：它決定最盛期的持續時間與等值曝火時間，與閃燃門檻分屬不同問題。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"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":33,"stem":34,"number":35,"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":37,"stem":38,"number":39,"year":11,"session":12},"fire-108-1-fire-science-012","建築物之中性帶高度受室內溫度、室外溫度及上下開口的影響，下列敘述何者錯誤？",12,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-108-1-fire-science-016","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？",16,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-108-1-fire-science-011","室內火災所產生的熱煙層由天花板向下沉降的時間直接影響逃生；以此觀點而論，下列何者較不利於逃生？",11,{"webId":49,"stem":50,"number":51,"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,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-014",113,"下列何者屬水蒸氣爆炸？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-014",112,"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？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-014",111,"普通木造建築物旁欲蓋 9 公尺高之建築物，其延燒係數為 3 級（係數為 0.15），其防火間隔應保持多少公尺？",{"webId":66,"year":67,"stem":68,"number":13},"fire-110-1-fire-science-014",110,"自然發火性物質中的原棉，主要是因為下列何種熱之蓄積而發火？",{"webId":70,"year":71,"stem":72,"number":13},"fire-109-1-fire-science-014",109,"火場溫度隨燃燒時間而逐漸升高，其空氣亦漸膨脹，空氣由外界流入該起火房間，同時熱煙霧也會從該起火房間流出。若忽略燃燒分解過程而產生之質量流率，建築物內部空氣溫度為 25℃，起火房間溫度為 800℃，流入起火房間之空氣體積流量為 1 m3\u002Fs，則流出起火房間之熱煙霧體積流量約為若干？",1785129967525]