2020 Virtual AIChE Annual Meeting
(319g) Pressure Drop in Bubbly Gas-Liquid Flows in Packed-Beds in Zero Gravity: Analysis of Experimental Results from the International Space Station
The Packed Bed Reactor Experiment (PBRE) is developed and flown on the International Space Station (ISS) to study two-phase flow in porous media which is fundamental for many space applications such as life support systems, and chemical/materials processing. In this work, pressure drop and hysteresis effects in gas-liquid flows through packed-beds in microgravity are experimentally studied for two types of packing materials. 3 mm spherical beads are randomly ï¬lled in cylindrical test sections of 60 cm long and 5 cm in diameter equipped with five equally spaced absolute pressure transducers. The experiments are designed to cover low gas-liquid flow rate range which is typical of actual water processing systems flown in space. The two-phase friction factor equation is presented as the sum of an Ergun-type single-phase friction factor and a "dynamic phase interaction term" that models the complex effects of introducing a gas phase. The best-fit constant for this term is experimentally obtained as CS=0.6 for the wetting glass packing and CS=0.15 for the non-wetting Teflon packing. It is concluded that the pressure drop depends on the packing wettability in the viscous-capillary regime (0.1 < Re*GS < 1, 1 < Re*LS < 10) and the capillary contribution is the dominant force contributing to the pressure drop for the wetting case whereas the viscous contribution is dominant for the non-wetting case. For both the cases, the transition from viscous-capillary to inertia dominated regime occurs at Re*LS â 30-50 and is nearly independent of the gas flow rate. It is also found that outside of the viscous-capillary regime, hysteresis effects that are often strong in normal gravity flows are very weak in microgravity. It means that in the absence of gravity, increasing and then decreasing the liquid (gas) flow rate at a fixed gas (liquid) does not lead to very different values for the pressure gradients.