Experimental results on pressure drop and gas hold-up for gas-liquid
flow through packed beds obtained from a second flight on the
International Space Station are presented and analyzed. It is found that
the gas hold-up is a function of the 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 and is found to be linear with the
superficial liquid velocity but is a much weaker function of the
superficial gas velocity. The capillary contribution is also a function
of the particle size and varies approximately inversely with the
particle diameter within the range of the test conditions.