固態硼氫化鈉溶解系統之模式建立與模擬

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Title:	固態硼氫化鈉溶解系統之模式建立與模擬
Other Titles:	Modeling and simulation of solid sodium borohydride dissolution systems
Authors:	羅永昇;Lo, Yong-Sheng
Contributors:	淡江大學化學工程與材料工程學系碩士班陳逸航
Keywords:	固態硼氫化鈉溶解系統;水管理;濃度邊界層厚度;Solid sodium borohydride dissolution systems;water management;concentration boundary layer thickness
Date:	2012
Issue Date:	2013-04-13 11:50:34 (UTC+8)
Abstract:	為了達到美國能源局(DOE)訂定的儲氫量7.5 wt.%，在此提出水管理的固態硼氫化鈉水解產氫反應系統。在本文中，固態硼氫化鈉錠溶解的水主要是質子交換燃料電池所產生水提供的。接著，建構數學模式去說明固態硼氫化鈉藉由擴散作用從錠的表面到水溶液中。使用”the equation of moment”解出濃度邊界層的厚度。濃度邊界層的厚度是跟擴散係數、水的流速及流動的距離有關。在求出濃度邊界層厚度後，在使用”Crank Nicolson method”去解NaBH4的質量平衡的方程式。求出的平均濃度與實驗數據有符合。為滿足50 W電能需求，本系統最理想的目標是獲得最小體積。本系統設計的三個變數分別為：硼氫化鈉錠的直徑、管內直徑及液位高度。以筆記型電腦所需電力50 W操作1 hr為目標，結果為：最小體積VT=16.69cm，管徑DR=2.5cm，錠直徑DS=2.2cm，液位高度xh=1.7cm 。 In order to achieve the hydrogen storage capacity 7.5 wt.% set by DOE (Department of Energy), the solid sodium borohydride hydrolysis reaction with water management was proposed. In this work, the solid sodium borohydride tablet was dissolved in recycled water which was generated from proton exchange membrane fuel cells. The mathematical model was built to describe the mass diffusion through the surface of the solid sodium borohydride tablet to the bulk water solution. The equation of moment method was used to solve and determine the concentration boundary layer thickness which is a function of diffusivity coefficient, velocity of water in the annular space and flow distance. After determining the concentration boundary layer thickness, the Crank Nicolson method was used to solve the material balance equation of NaBH4. The effluent average NaBH4 concentration of the vessel can be evaluated and fitted with our experiment data. For 50 W power demand the optimal objective of the system is to minimize the container size. Three design variables of the system are: The tablet diameter, cylindrical vessel diameter, and height of liquid. In order to generate 50W power for Notebook using around 1 hr, the minimum cylindrical vessel volume VT=16.69cm, cylindrical vessel diameter DR=2.5cm,the tablet diameter DS=2.2cm,height of liquid xh=1.7cm
Appears in Collections:	[Graduate Institute & Department of Chemical and Materials Engineering] Thesis

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