Gas-liquid flows through porous media in microgravity: Packed Bed Reactor Experiment-2

Modifications were made to the Packed Bed Reactor Experiment (PBRE) and flown on the International Space Station as PBRE-2 to eliminate external pressure oscillations at higher liquid flow rates and the packing diameter was reduced to increase the pressure gradient for lower flows. It is found that gas hold-up is a function of bed history at low liquid and gas flow rates whereas higher gas hold-up and pressure gradients are observed for the test conditions following a liquid only pre-flow compared to the test conditions following a gas only pre-flow period. Over the range of flow rates tested, the capillary force is the dominant contributor to the pressure gradient, which is found to be linear with the superficial liquid velocity but is a much weaker function of the superficial gas velocity and varies inversely with the particle diameter.