生物燃料電池是近年來較為新興的科技，大部分的研究仍著墨於實驗，因此本研究提出一個三維的數值模擬模型，希望能藉此對生物燃料電池有更多的了解，並能藉由簡單地改變操作參數或設計來提升性能。首先藉由比對實驗數據，我們的模型能夠準確預測實驗的電壓電流極化曲線結果，最大誤差不超過3 %。在此同時，我們的模型可以呈現整個電池的流場、反應物濃度分佈和生物活性的分佈。整體來說，電池中的反應物濃度在達到穩態時仍非常的高，但在接近生物膜反應區有顯著的下降，表示在同樣的流入下，電池還有很多進步的空間。除此之外，電池的角落都不利於生物活性，對於整個電流的生產貢獻趨近於零，原因包括較低的流量和邊界層阻礙反應物擴散。大部分的生物活性都集中在入口處，隨著前段生物消耗反應物再加上邊界層發展，生物活性往出口處持續地下降，但在接近出口處電極結束處有些微的回升。為了降低邊界層的影響，在增加流量50 %的情況下，可以提升最大功率7 %；降低深寬比的情況，則可以提升最大功率達9.6 %，這樣的結果顯現改變電池的物理操作參數，就有可能來提升電池的表現。另外，為了平均反應物濃度分佈，我們更改了不同的流進流出設計，藉此也能提升最大功率達11%，這樣的提升主要來自於整個電池的生物活性較為的平均分佈，說明生物燃料電池仍有許多的進步空間。

Microbial fuel cell is a relatively new technology that start to gain some tracktion over the past deacade, however, most of the studies focus on experiment. In this study, we constructed a 3D Microbial fuel cell (MFC) model that successfully predicts the voltage and current density polarization cure from the experiment with less than 3 % differences. Our model allowed us to take a look at the flow field, concentration distribution and active biomass distribution of the cell. From our observation, corners of the anode compartment are low to none in active biomass, meaning it does not contributes to current production due to poor substrate accessibility. In addition, the boundary layer develop from the leading edge of electrode also siginificantly affects the substrate diffusion to the biofilm and thus become a critical factor for power output. Generally, active biomass concetrates at around inlet but also experiences a slight increase when approaching outlet. When the flowrate is lower and the aspect ratio is larger, the boundary layer is thicker but can already result in a lower power output up to 14%. On the contrary, when the increase flowrate and aspect ratio, the maximu power output increase bt 7 % and 9.6 %, respectively, showing room for enhancement through physical parameters. Moreover, by merely changing the inlet design, aiming to break the boundary layer and enhance substrate distribution, we are able to achieve a 11% increase in power output. The improvement is derived from overall higher active biomass suggesting that we are not taking full advantage of the cell.

Chapter 1 Introduction 2
1.1 Background 2
1.2 Literature Review 3
1.3 Purpose 8
Chapter 2 Theory 10
2-1 General Background 10
2-2 Nernst-Monod Equation 10
2-3 Butler-Volmer Equation 12
2-4 Voltage Equation 13
Chapter 3 Materials and Model 16
3-1 Fudmental Assumptions 16
3-2 Governing Equation 19
3-3 Boundary and Initial Conditions 20
3-4 Method 21
Chapter 4 Result and Discussion 23
4-1 Grid Test 23
4-2 Validation of Proposed Model 23
4-3 Flowrate 32
4-4 Inlet 35
4-5 Aspect ratio 39
Chapter 5 Conclusion 42
Reference and Parameters 44

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