MODELING OF DIFFUSE CHARGE EFFECTS IN A MICROFLUIDIC BASED LAMINAR FLOW FUEL CELL Isaac B. Sprague 1 and Prashanta Dutta 1,2 1 School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington, USA 2 Department of Aerospace Information Engineering, Konkuk University, Seoul, Republic of Korea A mathematical model for laminar flow fuel cells including electrical double layer and ion transport effects is developed. The model consists of the Poisson-Nernst-Plank equations and the modified Navier-Stokes equations to account for the advection of species in the downstream direction. The generalized Frumkin-Butler-Volmer equation is used for the fuel cell kinetics. The finite-volume method is used to develop a system of algebraic equations from the governing partial differential equations, and a numerical algorithm is developed to obtain the results. The accuracy of the 2-D numerical simulation is validated against pub- lished results using a 1-D analytical solution. Numerical results show that the concentration distributions for both the neutral species and ions change in both the cross-stream and streamwise directions. An especially interesting result is the change in positive ion concen- tration within the electrical double layer along the streamwise direction. A study on the importance of the electric body force in the momentum conservation equations is also presented. It is found that the flow results are only affected by the electric body force term at the start of the electrodes and has a negligible impact on device performance results. This model allows us to study both kinetically active (electrodes) and inactive (insulated wall) regions for a microfluidic fuel cell. The mathematical model and numerical simulation will be particularly useful in analyzing the complex behavior that occurs in laminar flow electro- chemical devices where a minimum of two spatial dimensions must be considered and the electrical double layer and ion transport cannot be neglected. INTRODUCTION Fuel cell technology has existed since 1839, when it was first introduced as a new way to produce electrical power from chemical energy. Fuel cells are electro- chemical devices that combine fuel and oxidant sources to produce an electrical power. This is accomplished by separating a thermodynamically favorable reaction into two half reactions where ions are allowed to transfer from one half to the other through an electrolyte, while electrons are routed through a circuit. The half reactions are fuel oxidation at the anode and oxidant reduction at the cathode. Received 12 February 2010; accepted 19 August 2010. This research was partly supported by the 2010 KU Brain Pool Program of Konkuk University, Korea. Address correspondence to Prashanta Dutta, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, 99164-2920, USA. E-mail: dutta@mail.wsu.edu Numerical Heat Transfer, Part A, 59: 1–27, 2011 Copyright # Taylor & Francis Group, LLC ISSN: 1040-7782 print=1521-0634 online DOI: 10.1080/10407782.2010.523299 1 Downloaded By: [Dutta, Prashanta] At: 22:35 28 January 2011