The Dynamics of Liquid Sorbents in Open Capillary Channels

Direct contact liquid-gas sorbent beds offer unique benefits for spacecraft air quality control. In a recent ISS technology demonstration experiment (CSELS---Capillary Sorbent), two 16-parallel open capillary channel contactors plumbed in series demonstrated passive `thin film' control, modeling both absorption and desorption functions for a potential low-gravity gas scrubbing system for spacecraft. The open wedge-shaped channels mimic terrestrial falling film reactors by exploiting capillary pressure gradients instead of gravity. In this presentation we highlight the fluid mechanics of the process~with and without the effects of~CO$_{\mathrm{2}}$~absorption across the surface. We identify the limits of operation, stability, and transients for systems as functions of wedge geometry and working fluid thermo-physical properties. Rare analytical solutions are found that may be applied to enormous systems of~$n$-parallel channels. The analytical approach serves as the building block for massively parallel systems requiring large surface areas to achieve the desired performance