Experimental study on the flow field geometry of the PEM fuel cell bipolar plates: The effects of various shaped blocks embedded in serpentine pattern on cell performance

The flow field pattern is crucial in many aspects such as cost-efficiency (in terms of excessive fuel consumption), water management on the cathode side, and achieving a high cell performance. The studies on the reconnaissance of much more effective flow field design have been continuing for years. As a matter of fact, it may be succeeded with some manipulations on the flow area. The current research proposes to investigate the effects of blocks in various shapes and positions on the net power output by changing the shape of the channels in the flow field (FF). For this reason, semicircular and triangular blocks were machined on the serpentine channels and their short-term performances were compared with the conventional serpentine pattern. In addition to the related new FF designs, performance evaluation was made by using nickel foam placed to fill the inner part of the serpentine FF. First, ultimate operating conditions were optimized with the traditional serpentine FF. Then, the performance outputs of the proposed FF designs were compared under the same conditions assigned in the previous section. The single-cell performance tests yielded that the highest power density was ensured with nickel foam (NF)-serpentine FF with 0.267 W/cm2. This increment corresponds to a 38 % enhancement in the power output when compared to the classical serpentine-type FF. Triangular (T) and semicircular (S) obstacles increased the performance significantly. Each manipulation on the traditional serpentine FF affected the power output positively, essentially. The pattern structures of the diagonal semicircle (DS) and diagonal triangular (DT) FFs reduced both water evacuation ability and performance increase rate. NF-serpentine FF contact highly decreased the ohmic resistance level of the cell when compared to the other designs according to the impedance (EIS) measurements. In addition, a correlation was observed between the performance and pressure drop test results. The highest-pressure drop was recorded with NF-serpentine FF (4.225 kPa) whereas the lowest is conventional serpentine FF (0.55 kPa). Traditional serpentine pattern is famous for with high-pressure drop structure. Consecutively, the pressure drop tests proved that the manipulations increased the pressure level of the system directly.