Pore scale study of ice melting and multiphase flow in gas diffusion layer with porosity gradient in PEMFC

Abstract

An enthalpy-based multi-component multiphase flow model is established by using the lattice Boltzmann method (LBM), and the ice melting and liquid water flow behavior during cold start process in gas diffusion layers (GDLs) with porosity gradients of proton exchange membrane fuel cell (PEMFC) are captured. GDLs with five porosity gradients are considered to explore the ice melting efficiency, temperature distribution characteristics and liquid water transport. The results show that the ice melting rate is significantly affected by the porosity distribution. The model of porosity decreasing gradually from near catalyst layer to near channel side (M4) greatly improves ice melt efficiency by up to 61.44%, while the 'V' porosity gradient (M2) and the model of porosity increasing gradually from near catalyst layer to near channel side (M3) prolong the heating and melting time of 15.6% and 25.56% respectively. The arrangement of small porosity structure near the channel side enhance the convective and conduction heat transfer. The hydrophilicity of the surface of fibers is beneficial to ice melting but hinders the discharge of liquid water. Considering the ice melting efficiency and drainage performance, the GDL with porosity gradient can be used when selecting the auxiliary measure of inlet preheating.