Development Of Multi-Physics Coupled Model And Investigations On Heat And Mass Transfer In Gas Diffusion Layer Of PEMFC

Facing the transition to a green and low-carbon society,hydrogen has attracted continuous attention and has been one of the hot topics in energy research area.PEMFC has been considered as one of the most potentially alternative power devices in future applications,due to its high performance,low emission.Consequently,auto companies such as Toyota,Honda,and Shanghai Hydrogen Propulsion Technology,have already launched products in recent years,High-efficiency water and heat management is critical to improve the durability and lifetime of PEMFC.Researchers have paid great efforts on the water transport in the channel and GDL to achieve a better oxygen supply and water removal.By reviewing the research status of the heat and mass transfer in the porous electrodes,this study has suggested some potential research directions for future improvements.It was found that little attention has been paid on the vibration,compression,vapor condensation,coupled heat and mass transfer in the literature.Most of the studies did not consider the coupling of multi-physics,and they ignored the compression effects on the water and heat distribution inside GDL.On the basis of the limitations of the current research,considering the real operating conditions,the present study carried out numerical investigations after the reconstruction and compression of the 3D structural GDL using the stochastic method.This study has developed and implemented solvers which can solve various water and heat management issues on the open-source platform OpenFOAM.In this way,the multiphase flow,heat and water transfer problems can be properly addressed.The main research objectives in this study are summarized below:(1)Investigations on the GDL performance parameters.A surrogate model was obtained using the SVM and optimization process was conducted employing the genetic algorithm.High accuracy was found between the target and prediction samples after training and testing.Compared to the numerical simulation and experimental testing,the surrogate model can largely save the time and economic costs.This approach can be extended to solve different data-driven research subjects.(2)The effects of vibration conditions on the two-phase flow in GDL.By modifying the governing equations and adding vibration source terms,a numerical model was developed to study the vibration conditions on the water transport process.Besides,dynamic mesh technique has also been employed to compare.The water transport process in the GDL has been summarized.The amplitudes and vibration frequencies effects on the water transport has been explored.It was found that vibration in the vertical direction had a larger impact compared to that vibration in the horizontal direction.The water saturation presented sinusoidal changing under a high frequency vibration,while the periodical characteristics was weak under a low frequency vibration.(3)The vapor condensation and removal process in GDL.A validated phase change solver was developed and implemented in the OpenFOAM platform to simulate the vapor condensation process.Comprehensive simulations were carried out to analyze the GDL porosity distribution,compressed deformation,mass flow rate,local temperature and contact angle effects on the vapor condensation and transport dynamics.This study was significant to deepen our understanding on the vapor condensation process and water transport dynamics in GDL,which could further guide the GDL design and optimization.(4)The dry processes of the liquid water in GDL under the shutdown purge.A multi-component phase change solver was employed to investigate the effects of the gas mass flow rate and temperature difference on the dry processes.It was found that the liquid water was dry through the evaporation rather than removing in liquid form.Compared to the IP direction,water transport in TP direction will accelerate the dry processes.In addition,purge strategies were proposed based on different air intake temperatures and mass flow rates.(5)A gas-liquid-solid coupled model was developed and implemented in the opensource computational fluid dynamic platform OpenFOAM,which can simultaneously model the liquid water transport,vapor condensation,conjugate heat transfer,electric conduction and their interactions.The impacts of water transport on heat transfer were investigated.For the whole heat transfer process,the heat conduction was the major approach through the solid fibrous layers both in dry and wet GDL,while the accompanied heat conduction and convection during the water transport were also crucial in wet GDL.A very minimal impact can be observed from the electrical distributions,indicating the liquid water effects on the electrical conduction can be ignored.This investigation using the gas-liquid-solid coupled model can provide a realistic temperature distribution inside a GDL with rib structure,which is crucial to obtain the condensation water distribution and saturation.Therefore,this study aimed to optimize the water and heat management to improve the fuel cell performance.On the basis of the limitations of the current research,surrogate model of GDL performance parameters were obtained with machine learning;The effects of vibration conditions on the two-phase flow in GDL were discussed;The vapor condensation and liquid water dry processes were explored.A gas-liquid-solid coupled model was developed to achieve a comprehensive simulation of the "gaswater-heat-electricity-stress".This study is significant to guide the GDL design and optimization.