本文為金屬氫化物顆粒床有效熱傳導係數(effective thermal conductivity)量測與實驗分析。實驗反應容器設計為利用一維定常之熱傳方法並採用美國材料試驗協會(American Society for Testing and Materials, ASTM)量測固態材料熱傳導係數實驗設計準則，設計製作儲氫材料反應容器與實驗系統，成功的建立儲氫合金顆粒床(metal hydride granular bed)有效熱傳導係數量測系統。金屬氫化物儲氫容器整體的熱傳特性主要受到儲氫合金顆粒床本身之熱傳導之影響，因此，對儲氫床之整體有效熱傳導係數的掌握，對儲放氫之效率十分重要。由於儲氫床是以合金粉末顆粒之形式存在，熱傳特性包含了合金粒子間之接觸熱傳與粒子間空隙中之氣體影響，所以本研究針對不同供氫壓力探討儲氫床整體之有效熱傳導係數變化。 本實驗對象為LaNi5儲氫合金粉末，根據金屬反應容器在平均溫度約40?C下實驗結果，隨著供氫壓力之提升整體有效熱傳導係數會有提高之趨勢，並發現當壓力位於PCI曲線α相區時，有效熱傳導係數變化受到氣體壓力的主導，當進入到α+β區時，改由儲氫量主導有效熱傳導係數的變化。根據儲氫量變化與有效熱傳導係數間之關係發現，有效熱傳導係數幾乎隨儲氫量而線性變化。 透過實驗結果顯示，LaNi5儲氫合金粉末，在孔隙率0.58之情況下，實驗操作壓力範圍0.0001 – 18 bar，平均溫度40?C時，有效熱傳導係數之變化區間界在0.15 – 0.75 W/mK之間。 Heat transfer strongly affects the metal hydride reaction rates. Because metal hydride alloys used in practice are in the form of powders, the granular bed comprises the particles and void spaces between the powders. The effective thermal conductivity of the metal hydride bed therefore determines the heat transfer characteristics of the metal hydride storage vessel. This study aims to measure the effective thermal conductivity under different hydrogen supply pressures. The experiment reaction vessel was designed based one one-dimensional steady-state axial heat transfer by referring to the guideline of America Society for Testing and Materials (ASTM) for measuring the thermal conductivity of solids by means of the graded-comparative-longitudinal heat flow technique. A LaNi5 alloy granular bed was measured for the effective thermal conductivity with various hydrogen pressures. Results showed the effective thermal conductivity dramatically increased with increasing hydrogen pressure in the phase of the alloy pressure-concentration-isotherm curve. In the β phase however, the hydrogen contents dominated the change of the effective thermal conductivity. The effective thermal conductivity was almost a linear function of the hydrogen content. The LaNi5 powder bed with the porosity of 0.58 was shown to has the effective thermal conductivity ranging from 0.15 to 0.75 W/mK for hydrogen pressure changing from 0.0001 to 18 bar around 38?C.
