Fundamental study of design of small size DMFC by using Marangoni convection

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A fuel cell is expected as a source of clean energy in the various fields. A PEMFC is developed in the field vehicle. On the other hand, a DMFC is suitable for small size product such as note PCs and cell phones. However, method of methanol supply is serious problem to be solved because 1/10 size of DMFC is required compare with the present situation. At present, small size of pump is used for it. In order to shrink the size very much, new type of supply method must be developed. For this purpose, fundamental study was carried out for development of new type of methanol supply by using Marangoni convection. The following results were obtained ;(A) Effect of gas-liquid two-phase flow:Numerical simulation was carried out for the effect of CO_2 bubbles which was induced by chemical reaction during FC running on the Marangoni convection. Simulation results showed the bubbles disturbed the interface and suppressed the Marangoni convection. Also, it was found that the bubbles suppressed the chemical reaction on the catalysis and decreased electrical current density. By using this simulation code, calculation of limit current density is available.(B) Co-existence effect of thermal and solutal Marangoni convection:Effect of co-existence effect of thermal and solutal Marangoni convection on fluid flow was numerically investigated. It was found that thermal Marangoni convection determine the flow structure in the liquid. However, it was also found that solutal Marangoni convection was important for local structure of flow. Especially, velocity induced by solutal Marangoni convection was relatively slow because the concentration gradient became gentle as flow developed.