The focus of this work is to investigate transport phenomena in recently developed microscale fuel cell designs using computational fluid dynamics (CFD). Two microscale fuel cell systems are considered in this work:​ the membraneless microfluidic fuel cell and a planar array of integrated fuel cells.

A concise electrochemical model of the key reactions and appropriate boundary conditions are presented in conjunction with the development of a threedimensional CFD model of a membraneless microfluidic fuel cell that accounts for the coupled flow, species transport and reaction kinetics. Numerical simulations show that the fuel cell is diffusion limited, and the system performances of several microchannel and electrode geometries are compared. A tapered-electrode design is proposed, which results in a fuel utilization of over 50 %.

A computational heat transfer analysis of an array of distributed fuel cells on the bottom wall of a horizontal enclosure is also presented. The fuel cells are modelled as flush-mounted sources with prescribed heat flux boundary conditions. The optimum heat transfer rates and the onset of thermal instability are found to be governed by the length and spacing of the sources and the width-to-height aspect ratio of the enclosure. The transition from a conduction-dominated to a convectiondominated regime occurs over a range of Rayleigh numbers. Smaller source lengths result in higher heat transfer rates due to dramatic changes in Rayleigh-Bénard cell structures following transition.