Optimization of the structure and cathode operating parameters of a serpentine PEMFC with longitudinal vortex generators by response surface method

Abstract

An improved method based on a concept for enhancing heat and mass transfer based on longitudinal vortex system is proposed for optimizing the performance and water-thermal management of proton exchange membrane fuel cells (PEMFCs). A certain number of rectangular plates are added to the cathode channel of the serpentine plate to create the longitudinal vortex to enhance the diffusion of fuel gas, the discharge of water, and temperature distribution uniformity of the fuel cell. A series of numerical studies are conducted employing the response surface method to evaluate the effect of cathode operating parameters on the efficiency and power density of the fuel cell system. The results obviously suggest that the installation of twenty groups of Longitudinal vortex generators(LVGs) in the first four straight flow channels can enhance the mean current density by 5.02 % compared with the condition without LVGs. Meanwhile, LVGs in the cathode flow channel close to the inlet can also enhance the distribution uniformity of membrane temperature by 11.38 %, which can contribute to the diffusion enhancement of oxygen by 36.94 % at the cathode and the improvement of water distribution uniformity by 10.87 %. The main reason for this phenomenon is that the rectangular-plate longitudinal vortex generator can increase the local turbulence intensity of the fuel gas in the cathode channel; therefore, more fuel gas can be transported from the channel to the diffusion layer, leading to a greater current density, in addition to the fact that the generated longitudinal vortex system can assist the exiting of the generated water from the channel. In addition to these, increasing pressure or reducing temperature or relative humidity can enhance power density, while reducing relative humidity is beneficial for improving system efficiency.