為配合中鋼所成立之自主設計技術力專案推動團隊，本論文針對中龍#24 Didier-type 熱風爐之運作情形進行熱液動分析，以期提供中鋼設計、優化熱風爐之參考依據。此外，由於熱風爐處於長時高溫運作條件下，因此若需針對熱風爐爐內進行檢修時，必須將熱風爐冷卻才可進行施工，故本論文亦針對中鋼#34 KK-type 熱風爐進行冷卻散熱之初步分析，探討在不同進口流率下冷卻#34熱風爐所需耗費之時間。
針對中龍#24 Didier-type熱風爐之熱液動分析方面，本研究輔以中鋼提供之實際之操作條件做為邊界條件進行模擬，並且將模擬結果 與現場時計量測值進行比較，以驗證本研究之有效性。此外，為了能針對整個熱風爐運作過程進行數值分析模擬，需針對其結構進行一些簡化處理，簡化內容主要包含兩方面: (1)將熱風爐各部位沿厚度方向之多種材質所構成之壁磚等效為一種材質，且其性能參數均考慮為溫度之函數、(2)使用非平衡多孔性介質(non-equilibrium porous medium)取代實際多孔蓄熱磚磚(七孔磚)，用以簡化蓄熱磚與流體間之熱交換計算。
在Didier type熱風爐熱液動分析方面，以800K為初始溫度，並以一個週期(On gas + On blast)為單位進行循環計算，直至溫度與速度場達到準穩態 (quasi-steady-state)。通過模擬發現，在On gas 階段，煙氣從燃燒室經過拱頂和火橋到達蓄熱室時，拱頂之結構具有導流作用，致使火橋上方產生渦旋；而在On blast 階段，熱鼓風從蓄熱室經過拱頂與火橋到達燃燒室時，在燃燒室上段左半部亦會因為拱頂之導流作用有渦旋產生。在整個週期內爐內速度均隨溫度和流道截面積之變化而變化，在On gas 階段，燃燒室內隨著高度、時間增加管徑與溫度無明顯之變化，流速約為23.6 m/s，而在蓄熱室中，由於蓄熱磚吸熱之緣故，因此流體溫度隨流動方向降低，進而導致爐身內流速不同，其流速範圍介於6.9 m/s~14.1 m/s；在On blast階段，燃燒室之溫度亦無太大之差異，其流速約為7.8 m/s ，而蓄熱室內流體之溫度呈隨流動方向增上升之趨勢，其流速範圍介於2.16 m/s~4.9 m/s。同時，為了驗證Didier type熱風爐熱液動分析之有效性，將模擬之溫度與熱風爐實測操作過程中不同量測點之溫度進行比對分析。結果顯示，煙氣出口溫度、拱頂壁磚溫度及熱風出口溫度之計算最大誤差分別為4.2% 、6.4%、3.2%，均在10%以內。
對蓄熱磚而言，在On gas階段，煙氣溫度高於蓄熱磚之溫度，蓄熱磚從煙氣吸熱，蓄熱磚溫度隨時間的增加而增加；在On blast階段，空氣溫度低於蓄熱磚之溫度，因此蓄熱磚向冷鼓風放熱，蓄熱磚溫度隨時間的增加而減小。而在整個週期內，蓄熱磚溫度均隨著高度的增加而上升，且蓄熱磚與流體之溫差約為50~80℃。對壁磚而言，熱風爐各部位之溫度均表現為On gas階段溫度高於On blast階段，整個熱風爐在一個週期內之溫度範圍為200～1350℃，其中，蓄熱室各部位之溫度變化較大，且隨高度和時間之變化而明顯改變，內外壁溫差範圍介於200～1000℃，而燃燒室、拱頂及火橋隨時間和位置之溫度變化不大，內外壁溫差約介於1100～1300℃之間。
在KK type熱風爐冷卻分析方面，本論文以準穩態之On blast之最後一秒溫度做為初始條件，並探討四種不同進口邊界條件(3.5 kg/s、7 kg/s、14 kg/s、28 kg/s)其冷卻時間之差異，根據結果發現，蓄熱室各監測點之初始溫度與高度成正比，因此其冷卻至 亦耗時越長，此外，燃燒室冷卻之效率將比蓄熱室來的更優異。蓄熱磚則由於其與流體之熱交換效率較壁磚佳，因此蓄熱磚冷卻速度比壁磚還快。在所有監測點中，最不易冷卻之位置為拱頂以及熱風爐頸部位置，因此能以這兩處為判斷基準，藉此判斷熱風爐是否已達冷卻。

The hot blast stove is one of the most important equipment in the blast furnace iron making process ,the structure of which is composed of four main parts : (1) checker chamber,(2) combustion chamber,(3) dome, and (4) cross-over. The operating process is cyclic. One cycle consists an on-gas period and an on-blast period. In this study, it’s divided into two parts. The first part focus on temperature and velocity distribution in Didier type hot blast stove during the operating process. The second part is investigated to compare the cooling time of Krupp-Koppers type hot blast stove under different inlet boundary condition. The results are described as follows:
In the thermal hydraulic analysis of Didier type hot blast stove ,the simulation results are compared with the in-situ data, and the maximum error is found to be lower than 10%. The fluid velocity in the hot blast stove is varied with different temperature and flow cross-sectional area. The simulation also show that the fluid(gas) temperature is higher than solid(checker) in checker chamber during on-gas period, and the temperature difference is about 50~60℃.But during on blast period, the fluid(blast) temperature is lower than solid(checker), and the temperature difference is about 70~80℃. In a cycle, the temperature range of the inner wall is between 200℃ and 1350℃. The temperature varies greatly with changes of height and time in checker chamber, the inner and outer wall temperature difference is 200~1000℃, but in the dome, cross-over and combustion chamber, the temperature changes little with time and location, the temperature difference is 1100~1300℃.
Regarding the cooling analysis of Krupp-Koppers hot blast stove, this study uses the last second of on blast period as the initial condition, and discusses the time required to cool hot blast stove to 100℃ with different inlet boundary condition(3.5 kg/s、7 kg/s、14 kg/s、28 kg/s). According to the simulation results, in the checker chamber, the initial temperature is proportional to the height, so the required cooling time in checker chamber is also proportional to the height, and the combustion chamber cooling efficiency is higher than checker chamber. Among the whole hot blast stove, the most difficultly to cool positions are dome and chamber neck, that need cost longest time to cool to 100℃, therefore ,these two locations can be used as criterion to determine whether the hot blast stove has been cooled down.
Key words: thermal hydraulic, Didier-type hot blast stove, Krupp-Koppers type hot blast stove

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