Simulation of Heat and Mass Transfer during hydrogen absorption in a storage canister Equipped with a Heat Pipe
| Autor: | Yuan-Jen Chen, 陳元任 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 A simulation study of the hydrogen absorption processes using LaNi5 hydrogen storage alloy is presented. The hydrogen storage canister is assumed to comprise two physical domains, which includes an expansion volume atop an alloy bed. The expansion volume provides the spare space which allow for alloy to expand during the absorption processes. The alloy bed is treated as a porous medium. The energy equations are used to describe the temperature changes induced by the heat release during the hydriding processes which causes the alloy''s temperature to change with time. The continuity equations are adopted to describe the mass balance between the alloy and hydrogen. The Brinkman-Forchheimer and Navier-Stokes equations are used to describe the gas flow within the porous medium and expansion volume, respectively. The mathematical model developed is solved using a finite element code, COMSOL Multiphysics 3.5a. To verify the model, results from simulation are compared with experimental data. Results show that in the same conditions, the canister with heat pipe and fins absorbs hydrogen faster than the hollow one. This is because the heat pipe and fins help transfer heat inside out, so the equilibrium pressures of the alloy would be lower and the absorbing rates would be higher in the finned canister than in the hollow one. Results also show the entire period may be divided into four stages according to the hydrogen flow patterns, which is the outcome of the competition between the inertia and buoyancy forces in the expansion volume. Parameter analyses are also performed on the absorption rates. Results show the larger the diameter and thickness of the fins, the faster the absorption rates. The model can be applied to evaluate the request for the power limit of the instored heat pipe. The heat pipe would work when the heat transfer rates through the pipe are less than the power limit. Otherwise, the heat pipe would increase the absorption rates only in the very final stage of the hydriding processes. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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