儲氫合金粉末在儲氫過程中為放熱反應，當其溫度超出反應作用溫度時，則儲氫反應停滯。因此找尋儲氫系統內最佳熱管理方式，以縮短儲氫反應時間，進而提高儲氫效率是改善儲氫系統之首重課題。一般而言儲氫系統相關設備與耗材昂貴且高壓氫氣危險性高，但幸運的是儲氫粉末與矽膠之巨觀吸附反應相似，低成本、低危險性之矽膠相當適合作為多孔性材質吸附反應器熱管理實驗研究之替代介質。因此在本研究中我們利用矽膠顆粒，重現多孔性吸附反應器之熱傳表現，期待間接解決儲氫系統內多孔性熱傳問題，此外相關研究結果也可作為矽膠吸濕器之設計依據。
具體而言，本研究將已知空氣流量與入口平均濕度之濕空氣通入填滿矽膠之反應器內，進行矽膠吸附反應。反應期間記錄反應器壓力、內部溫度、內外壁溫度與出入口空氣之溫度、濕度、流量。接著以熱傳角度解釋矽膠系統內特定一點之溫度曲線，並導入簡化數學模型解釋矽膠系統之升溫現象。之後比較矽膠系統內中心軸上三個不同位置之溫度大小，並輔以熱擴散方程式模擬中心軸上溫度分布，解釋最高溫度發生在中間段矽膠之原由。最後改變入口平均濕度、反應器平均壓力與空氣流量，觀察這三個變因對於溫度曲線、出口濕度、吸附水量與吸附熱功率等影響。結果顯示在矽膠系統內若反應器平均壓力越大，入口平均濕度越高，則吸附水量越多，吸附熱功率越高，其巨觀表現與儲氫系統相似。因此我們在後續研究中，若能在矽膠系統內找到一最佳熱管理方法以增進其吸濕與脫濕性能，期待能以相同方法應用在儲氫系統內，進而改善儲氫系統內部熱傳，縮短儲氫時間。

The hydriding process in a hydrogen storage system involves a reversible exothermic chemical reaction. The heat released during the reaction process has a direct effect on the hydrogen supply characteristics and therefore must be carefully managed. However, in investigating and enhancing the performance of hydrogen systems, experimental cost and safety are major concerns. Therefore, metal hydride powder is substituted by silica gel in our experimental study of the thermal management of porous adsorption reactors. The temperature variation with time within reactors in both hydrogen system and silica system are similar. Thus, relatively safe silica gel system is a proper material to mimic the thermal behavior of hydrogen storage system.
In the present study, air with a known humidity and flow rate flows into a reactor filled with silica gel and the temperature, pressure, flow rate and humidity are measured both within the reactor and at the reactor outlet as the exothermal chemical reaction proceeds. The heat transfer characteristics at a point in the reactor are explained by physical arguments, and then a simplified mathematic model is constructed to support the physical arguments. Temperature at three axial positions in silica system are shown and the heat diffusion equation is employed to interpret the temperature variation in axial positions. The temperature variation, adsorption heat power, adsorption mass and humidity of outlet air under different conditions are shown and interpreted on physical grounds. The obtained results show that the moisture adsorption rate and adsorption heat power increase as the average reactor pressure and inlet humidity increase. Since the heat transfer characteristics in silica gel system and hydrogen system are similar, by improving the heat transfer in a silica system, the heat transfer problem in a hydrogen system can also be solved indirectly.

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