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

Abstract

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.

Hydrodynamics of bubble flow through a porous medium with applications to packed bed reactors

“…In experiments on two-phase flow through a PBR, the gas and liquid phases are injected at fixed flow rates at the inlet, which in turn determines the prevalent flow regime that will be observed in the PBR. [9][10][11] Since a simulation of an entire PBR is computationally expensive, we simulated bubble flow in the PBR REV that we constructed in Section 2.1.…”

“…Two‐phase flow through a PBR under microgravity conditions has been of particular interest because, in these conditions, gravity is no longer a dominant force in setting the displacement behavior. Based on experimental characterizations 9–14 previous work developed empirical models for the streamwise pressure drop, liquid holdup, and flow regime diagram 12,15–17 for gas‐liquid flow through PBRs in microgravity conditions.…”

“…Taghavi et al 10 extended the previous studies of gas-liquid flows in PBRs under microgravity conditions to longer-duration runs and smaller packing diameters, and they considered different gas and liquid preflow conditions. In addition to the dispersed bubble and pulse flow regimes, Taghavi et al 10 also observed regimes of large bubble flow and gas channeling. Due to the smaller packing diameter, the influence of capillary forces and, hence the overall pressure drop, was larger than that measured in the earlier experiments by Motil et al 9,11 More recently, Zhang et al 14 used a combination of experiments and two-fluid modeling to understand the pressure drop and liquid holdup trends with varying gas and liquid flow rates for different bead (or packing) sizes and liquid properties.…”

The international space station packed bed reactor experiment: capillary effects in gas-liquid two-phase flows

“…NASA funded a series of experiments to develop a fundamental understanding of how PBRs perform in the microgravity environment. Two separate test series were initially conducted on a reduced gravity aircraft test platform which limits the low gravity test duration to <20 s 7 followed by two additional test series, named the Packed Bed Reactor Experiment (PBRE), on the International Space Station (ISS) 8 , 9 which allowed for much longer duration testing at very low (micro) gravity conditions.…”

“…The second series of the PBRE experiments (PBRE-2) 9 was essentially a reflight of the original PBRE except for a smaller packing size and several modifications to improve the accuracy and control of the flow loop. Moreover, both gas flush and liquid flush pre-flows were used before the tests.…”