Optimization for Fuel Cells/Fuel Cell Stacks Using Combined Methods – CFD Modeling Analysis, and Experiments

by Hong Liu

Institution: University of Arizona
Year: 2013
Keywords: Fuel cell stack; Numerical Model; Optimization; Aerospace Engineering; Experimental test
Record ID: 2011893
Full text PDF: http://hdl.handle.net/10150/297027


Fuel cells are one of most environmental friendly energy sources; they have many advantages and may be used in many applications from portable electronic devices to automotive components. Proton exchange membrane (PEM) fuel cells are one of most reliable fuel cells and have advantage such as rapid-startup and ease of operation. This dissertation focuses on PEM fuel cell stack optimization based on operation experimental research and numerical modeling study. This dissertation presents three major research activities and the obtained results by the Ph.D candidate. A novel stack architecture design is introduced in order to decrease mal-distribution and non-uniform output performance between individual cells in order to improve the stack performance. Novel stack architecture includes a novel external bifurcation flow distribution delivery system. One major issue of uniform distribution of reactants inside individual fuel cells and between fuel cells in a fuel cell stack is solved by the novel stack architecture design. A novel method for uniform flow distribution was proposed, in which multiple levels of flow channel bifurcations were considered to uniformly distribute a flow into 2ⁿ flow channels at the final stage, after n levels of bifurcation. Some detailed parameters such as the flow channel length and width at each level of bifurcation as well as the curvature of the turning area of flow channels were particularly investigated. Computational fluid dynamics (CFD) based analysis and experimental tests were conducted to study the effect of the flow channel bifurcation structure and dimensions on the flow distribution uniformity. Optimization design and factors influential to the flow distribution uniformity were also delineated through the study. The flow field with the novel flow distribution was then considered to be used in a cooling plate for large fuel cell stacks and a possible method for cooling electronic devices. Details of the heat transfer performance, particularly the temperature distributions, on the heating surface as well as the pressure losses in the operation were obtained. In the second part of the research, experimental testing, analytical modeling, and CFD methods were employed for the study and optimization of flow fields and flow channel geometry in order to improve fuel cell performance. Based on the experimental results, a serpentine flow field is chosen for CFD and modeling analysis. Serpentine flow channel optimization is based on the parametrical study of many combinations of total channel width and rib ratio. Modeling analysis and in-house made computational code was used to optimize the dimensions of flow channels and channel walls. It is recommended that cell channel design should use a small total channel width and rib ratio. Proton exchange membrane fuel cells were fabricated based on the optimization results. Experimental tests were conducted and the results coincided with the numerical analysis; therefore, small total width and rib ratio design could significantly improve the fuel…