ABSTRACT Flow field design in PEM fuel cells has an important influence on both the power density and efficiency of fuel cell systems. In order to effectively utilize the active area, flow distribution and current density should be as homogenous as possible. In addition, pressure losses should be minimized. The main objective of this work is to provide a comprehensive study of the flow field characteristics for different parallel flow channel configurations. The investigated channel configurations are parallel with various cross-sectional configurations. For each channel configuration pressure drop, species mass fraction, velocity, and current distributions are numerically predicted. In addition, performance curves are presented and discussed. The predicted performance parameters are compared with the corresponding available experimental data. Based on the computed results the optimum channel design is selected. Detailed results are presented and discussed. The present work would help PEM fuel cell manufacturers, companies and researchers to choose the optimum configuration for their applications and products to achieve the best possible performance.

A new criterion has been developed to predict the onset of liquid (heavier fluid) entrainment from a stratified two-phase region. The criterion was developed based on the local instability of the interface between two fluids due to the suction effect associated with the discharging of the lighter fluid. To validate the proposed criterion, comparisons were conducted between the measured critical height at the onset and those predicted using a three-dimensional analysis of the flow through two configurations: (1) a single branch mounted on an inclined wall with an inclination angle ranging between −90° and + 60° and (2) dual branches mounted on a vertical wall with the plane passing through the branch centerlines and inclined with an angle α ranging between 0° and 60°. Comparisons demonstrate a very good agreement between the predicted and the measured values for both single and dual branches. This verifies that the onset of liquid entrainment mechanism occurs due to local flow instability of the interface, analogous to Rayleigh–Taylor instability.

In this work, carbon steel surface was coated with Al2O3–40 wt% TiO2 composite using thermal spraying method. The tribological properties of the plasma-sprayed Al2O3–40 wt% TiO2 coating were investigated with a tribometer (pin-on-disc) to evaluate and compare the wear properties of coated and uncoated samples under different loads. Additionally, cumulative weight analysis was done to compare wear loss. The results indicate significant anti-wear improvement with an increase in TiO2 from 13 wt% to 40 wt%. The corrosion on coated and uncoated samples was analyzed using AC and DC methods, namely open circuit potential from potentio-dynamic polarization and electrochemical impedance spectroscopy in 3% NaCl solution for 20 days.