Mg2Ni儲氫合金之儲氫罐吸放氫熱流分析及儲氫罐熱傳增強設計; Thermal-Fluid Behavior and Design of Heat Transfer Ehancement for Mg2Ni Hydride Storage Canisters

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题名:	Mg2Ni儲氫合金之儲氫罐吸放氫熱流分析及儲氫罐熱傳增強設計;Thermal-Fluid Behavior and Design of Heat Transfer Ehancement for Mg2Ni Hydride Storage Canisters
作者:	林琪翔;Ci-Siang Lin
贡献者:	能源工程研究所
关键词:	氫氣;金屬氫化物;儲氫罐;Mg2Ni，;metal hydride;Mg2Ni;hydrogen;hydrogen storage canister
日期:	2009-06-25
上传时间:	2009-09-21 11:30:46 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本文研究針對Mg2Ni儲氫合金在儲氫罐內吸放氫反應的模擬分析，探討儲氫罐吸放氫的熱流行為，並且比較典型圓柱型儲氫罐、同心圓柱型儲氫罐與添加鰭片同心圓柱型儲氫罐三者之合金平均溫度和吸放氫反應速率的差異，了解儲氫罐體與合金的熱傳效率對於整體儲氫合金吸放氫反應的影響。首先，依據線性最小平方迴歸法擬合文獻實驗數據，求得Mg2Ni儲氫合金吸放氫反應的合金平衡壓力與反應速率方程式，將所求得的Mg2Ni儲氫合金參數套入儲氫罐數學模型。儲氫合金吸氫過程合金粉末膨脹；放氫過程合金粉末收縮，所以本文將儲氫罐數學模型分為膨脹區與合金區，此外同心圓柱型儲氫罐加入計算中空管流體溫度的一維能量方程式，並在添加鰭片同心圓柱型儲氫罐增加計算鰭片溫度的能量方程式，以考慮中空管流體和鰭片對於儲氫合金溫度與吸放氫效率的影響。結果顯示典型的圓柱型儲氫罐不論是吸氫過程或放氫過程都無法在2小時內到達整體儲氫合金反應結束，但藉由儲氫罐體型式的修改，增加儲氫罐熱傳效果，添加鰭片同心圓柱型儲氫罐可在6000秒左右完成吸放氫反應，所以儲氫罐外型的修改可以明顯改善Mg2Ni儲氫合金原本緩慢的吸放氫反應速率。若是再將儲氫罐操作環境因素改變，如在吸氫過程降低環境溫度、增加入口壓力或是加快中空管冷卻流體的速度；放氫過程提高環境溫度、降低出口壓力或是加快中空管加熱流體的速度都可進一步加速吸放氫反應的進行。最後經由改變儲氫罐內部鰭片外型發現，其加強熱傳效果主要是由鰭片體積大小所控制。 A study of the hydrogen absorption and desorption processes using Mg2Ni hydrogen storage alloy is presented for investigation on the thermal-fluid behavior in canister and influences of canister geometry. Absorption and desorption reaction rates and equilibrium pressures are calculated by fitting experimental data in literature using least-squares regression. Then, the fitted parameters are used in the simulations for the thermal-fluid behavior of hydrogen storage canisters. Since the alloy powders will expand in absorption, and shrink in desorption, the canisters in question comprise a metal bed and expansion volume. To enhance heat transfer, we consider the canisters to be equipped with a air pipe at the centre line and/or with internal fins. Simulation results show the bare cylindrical canister can not carry out during two hours absorption or desorption reactions, but the canister with the addition of a concentric heat exchanger pipe with fins can complete absorption or desorption reactions during about 6000 s. Results also show the reaction rates can be further increased by adjusting working parameters For absorption processes, it benefit by reducing surrounding temperature, increasing inlet pressure or increasing flowing air velocity. For desorption processes, the reaction rate can be increased by increasing surrounding temperature, reducing outlet pressure or increasing flowing air velocity. Finally, adjusting the internal fin volume shows that it is the fin volume that principally affects the heat transfer enhancement of the hydride canister.
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