Study on the Differences in Heat and Mass Transfer Within Proton Exchange Membrane Electrolytic Cell Under Microgravity and Terrestrial Conditions

The absence of gravity in microgravity environments leads to a unique gas-liquid flow behavior in water electrolytic cells compared to terrestrial conditions, which in turn affects the electrochemical performance of the system. In this study, a two-dimensional nonisothermal two-phase flow stationary model was developed to examine the distribution of gas-liquid phases and temperature variations in proton exchange membrane (PEM) water electrolytic cells under microgravity conditions. The effects of microgravity and terrestrial gravity on the cell performance were directly compared. Results indicate that under terrestrial conditions, gravity enhances gas velocity and promotes faster vertical gas movement. However, as voltage increases, the disparity in average velocity and hydrogen concentration distribution between microgravity and terrestrial conditions diminishes, while the difference in temperature distribution becomes more pronounced. The observed performance differences under microgravity are primarily due to the reduced hydrogen flow rate within the cathode catalyst layer. A significant difference in electrical performance at low voltages is observed, whereas only a minor difference is noted at high voltages. Furthermore, as the operating temperature increases, the difference in electrical performance between microgravity and terrestrial conditions becomes more pronounced.