Experimental study of the S-shaped flow fields in proton exchange membrane fuel cells

•A series of S-shaped flow fields with different R and H are designed and verified by experiments.•Decrement in R or increment in H can promote the cell performance within the range of machinability.•The optimum S radius is 17.4 mm by trading off the performance and manufacturing possibility of the cell. Flow fields play an important role in performance enhancement of a Proton Exchange Membrane Fuel Cells (PEMFCs). However, the weak mass transport ability of the conventional parallel flow field seriously affects the cell performance, especially at high current density. In this work, a series of S-shaped flow fields are designed and experimentally verified. The effects of key design parameters, such as the S radius (R) and the S length (H), on the cell performance are investigated in detail by recording the polarization curves under different cathode relative humidity (RH) levels and stoichiometric ratios. The results indicate that the small R and large H are beneficial to the promotion of cell performance owing to the increased turbulence and decreased liquid water content in the cell, which is also proved by the electrochemical impedance spectroscopy (EIS). However, the pressure drop significantly increases at the same time, which affects the output ability of the cell. Considering the net output capacity and the processing processing possibility, the cell with the S radius of 17.4 mm and the S length of 40 mm exhibited the peak power density of 1.02 W cm−2, with 15% higher than the CPFF (870 W cm−2).