Numerical investigation on a vanadium microfluidic fuel cell for chip-level combined cooling and power applications

Vanadium microfluidic fuel cells (MFCs) offer high power density and low cost by eliminating the need for ion-exchange membranes and noble metal catalysts, making them promising for on-chip combined cooling and power (CCP) applications. However, previous numerical models for vanadium MFCs generally adopt the isothermal assumption, neglecting the significant temperature variation induced by reaction heat and joule heat, limiting the accuracy of performance prediction and the understanding of thermal-electrochemical coupling mechanism. To address this research gap, this work develops a non-isothermal vanadium MFC model that incorporates the local temperature dependence of electrolyte density, viscosity, diffusion coefficient, ionic conductivity, reaction rate constant, and equilibrium potential. Compared with conventional isothermal model, the non-isothermal model predicts up to 5.57% higher maximum current density, revealing a systematic underestimation of cell performance by isothermal approaches. When integrated with a heating chip, the model identifies a fundamental trade-off that higher electrolyte flow rates improve chip cooling but reduce MFC power output due to limited temperature rise. To resolve this dilemma, structural modification of the vanadium MFC is further investigated. It is found that reducing the channel thickness enhances cooling but degrades power density, whereas relocating the current collector from inlet to outlet improves power density by 20.6% without compromising cooling performance. These findings demonstrate that non-isothermal modeling is essential for accurate vanadium MFC simulation. Moreover, the current collector repositioning offers a simple yet effective strategy for balancing cooling and power of vanadium MFCs in chip-level CCP applications.