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Faculty Sponsor

Dr. Donald Mueller

Department/Program

Department of Civil and Mechanical Engineering

Abstract

Fuel cells are energy storage devices analogous to batteries in which electrochemical energy is directly converted into electrical energy. The main difference between a fuel cell and a battery is that a fuel cell is an open system allowing for chemicals to flow through while a battery is a closed system. As a consequence, a fuel cell can be turned off by simply stopping the flow. Fuel cells are also very energy dense, due to the fact that it is possible to store the chemicals that flow through them in separate tanks. Additionally, fuel cells do not pollute and, in theory, have a high current efficiency, making them an ideal long-lasting, flexible power source.

Research in direct borohydride-hydrogen peroxide fuel cells is still in its early stages, but results have been promising and the assembly process of a low-cost stack design needs to be investigated. This paper concentrates on the development of a computational fluid dynamics model for the flow in a fuel cell with ionic potassium borohydride as the fuel and hydrogen peroxide as the oxidizer. Once this model is developed and verified, it is used in conjunction with the system chemistry to determine the maximum number of cells that can be stacked and the corresponding flow rate that allows every cell to produce power without running out of reactant. The solution is dependent on the current per square centimeter produced by test cells. The results of this study show that a test cell producing 0.4 A/cm2 can be scaled up to a stack of 15 cells with a flow rate of 115 ml/min using the analyzed stack design. Furthermore, a detailed analysis of the internal flow through a single cell is conducted to determine possible locations for design improvement to accommodate a large number of high-power stacks (50 or more cells). These results show that the present cell design is adequate for initial stack testing, but not for making large high-powered stacks. Refinements of the fuel cell design will need to be done in the future to allow for more cells to be stacked for higher power outputs. The most important issue to address is reduction of the differential pressure at the inlet and outlet of the cell by eliminating the use of narrow tubing.

Disciplines

Urban, Community and Regional Planning

Flow Analysis In aDirect Borohydride-Hydrogen Peroxide Fuel-Cell Stack

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