Study of two-phase flow pressure drop characteristics in Proton Exchange Membrane (PEM) fuel cell flow channels of different geometries

One of the major challenges for proton exchange membrane (PEM) fuel cells is the management of water, produced as a byproduct of the electrochemical reactions. The buildup of liquid water within the gas flow channels creates distinct two-phase flow patterns. These two-phase flow patterns lead to a pressure drop across the channel by creating resistance to the flow of reactants. The accurate prediction of liquid and gas two-phase flow in PEM fuel cell flow channels is of utmost importance, as it can be used as an in-situ diagnostic tool for the investigation of the liquid water amassed within the gas flow channels. The geometry of the gas flow channels have been found to have influence on the pressure drop characteristics, and is considered as means of controlling the two-phase flow pressure drops. In this thesis, pressure drop measurement experiments are performed in ex-situ PEM fuel cell flow channels. Both single phase and two-phase flow pressure drops are measured for mass qualities of 0.819 and 0.850, corresponding to stoichiometric ratios of 1.2 and 1.5, and for a current density range of 0.2-4 A/cm2. Experiments are performed for two separate minichannel geometries – one having rectangular geometry, the other having semi-circular geometry. Water injection was done at a single point in the flow channel. The measured pressure drops were then compared with the values obtained using the empirical two-phase flow pressure drop model for application in PEM fuel cell, proposed by English and Kandlikar. Comparison is also made between the experimental pressure drops for the rectangular and semi-circular channel