壓擠式微型電動力電池能源轉換效能之理論分析與探究

Theoretical investigations on the performances and energy conversion efficiencies of squeeze flow electrokinetic micro-batteries

楊博文(Pao-Wen Yang)

指導教授 ： 黃信富

國立臺灣大學/工學院/機械工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.11283

摘要

本篇論文以傳統流道式壓力驅動流微型電動力電池之概念作為基礎，提出以擠壓或壓縮流道空間之方式，作為電動力發電系統中工作流體之驅動力，並分析二維系統以及軸對稱圓盤系統，壓擠式電動力電池所能產生之電流大小與能源轉換效率。同時，為提升壓擠式電動力電池系統之發電表現，吾人在邊界上引入了線性耐威滑移條件(linear Navier slip condition)以探討不同滑移條件對於本文所提出之電池系統其發電效能及表現之影響。在計算之前，先假設流道長遠大於流道之間隙，並以潤滑理論簡化統御方程式以利計算。由於壓擠式電動力電池之發電過程為動態，本篇論文將結果分為兩部分討論：壹、分析發電過程中的某一瞬間，發電系統內部流況、壓力分佈、電場分布以及所能產生之電流大小與能源轉換效能，以及貳、分析以固定移動速度以及固定外力兩種擠壓方式，分析系統內部的流場、壓力場、電場以及所能產生之電流大小與能源轉換效能如何隨著系統壓縮之過程而變化。研究結果指出，當外接電阻與壓擠式電動力電池本身內電阻相同時有最佳的能源轉換效能，且當發電系統為二維系統時，不同的外接電阻值皆有一個與其相匹配、使得壓擠式電動力電池有最佳能源轉換效率的流道長。另一方面，由發電系統所能產生的電流大小以及能源轉換效能之分析結果，皆證明了邊界上線性耐威滑移條件之引入能有效提升壓擠式電動力電池之發電表現。本文最後將壓擠式電動力微電池與傳統壓力驅動流電動力微電池各自之發電效能進行比較，證明壓擠式電動力電池有著較好的能源轉換效能，也期盼未來壓擠式電動力電池能因此被廣泛應用。

關鍵字

微電池 ； 壓擠流 ； 電動力 ； 流動電位 ； 微流道 ； 線性奈威滑移條件

並列摘要

Based on the concept of pressure-driven flow electrokinetic micro-battery, in this thesis, we present a brand new perspective, i.e., squeeze flow electrokinetic micro-battery, and analyze the magnitude of the streaming current generated as well as the energy conversion efficiency of the squeeze flow electrokinetic micro-battery system. Two types of micro-channel geometries are considered: one is the two-dimensional (2D) parallel plate model and the other is the axis-symmetric cylindrical disk model. To improve the performance of power-generation, the linear Navier slip condition on the flow velocity field is employed in the present study such that variations in the streaming current and energy conversion efficiency can be investigated for different slip parameter conditions. We assume that the length of the microchannel is much greater than the gap between the upper and lower plates or disks of the flow channel so that the lubrication approximation can be applied to simplify the governing equations and the process of calculation. Because the energy generating process of the squeeze flow electrokinetic micro-battery is a dynamic process, our results are discussed under two general themes: (i) We choose an instant during the dynamic process and analyze the velocity profile, pressure distribution, and electric field in the micro-battery system, as well as the generated current and the power transferring efficiency at that instant. (ii) We analyze the whole dynamic process and discuss the variations in the velocity field, pressure field, and electric field inside the micro-battery system, as well as the variations in the magnitude of the generated current and the power transferring efficiency during the squeezing process under both constant squeeze force and squeeze velocity conditions. The result shows that the best energy conversion efficiency is obtained when the external load resistance is equal to the inner resistance of micro-battery. Furthermore, for a given load resistance, there exists a channel length which gives the most efficient energy conversion performance associated with this resistance. Besides, all the results point out that applying the Navier linear-slip condition on the hydrodynamic boundaries substantially improves the energy conversion efficiency. Finally, we compare the respective energy efficiencies of the traditional pressure-driven flow electrokinetic micro-battery and the squeeze flow electrokinetic micro-battery and show that the squeeze flow electokinetic micro-battery has a better energy conversion performance.

並列關鍵字

micro-battery ； squeeze flow ； electrokinetic ； streaming potential ； micro-channel ； linear Navier slip condition

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