Modeling of mass transfer in a T-shaped microfluidic fuel cell

Abstract

The development of microelectronic devices has increased the need for a power supply with high power density for long-term operation. In this article, firstly, the microfluidic fuel cells (MFCs) have been introduced, secondly, due to the significant effect of mass transfer on their performance, mass transfer in these fuel cells has been investigated. MFCs have small dimensions and simple geometry, and usually, formic acid and oxygen dissolved in sulfuric acid are used as fuel and oxidizers, respectively. To model the MFC, the equations of continuity, momentum, and mass transfer have been solved in three-dimensional by Open-Foam open-source software and validated with the results available in the references. From Fick's equation has been used to calculate rate of diffusion and from the Butler-Volmer equation has been used to calculate rates of electrochemical reactions in catalyst layers. Preliminary results indicate that the performance of this fuel cell is greatly limited by poor fuel utilization, which is consistent with the experimental data. The flow is fully developed in this short distance from the inlet, and in the fully developed area, the ratio u_max⁄u ̅ is equal 2.1. The mixing zone located at the interface of fuel and oxidizer is in the shape of an hourglass in cross-section, and with increasing the inlet velocity, its thickness decreases along the channel. Also, as the flow moves along the channel, the thickness of the layer with a low concentration near the electrodes increases.