Comprehensive Digital Twin of a Microfluidic Electrochemical Reactor to Optimize the Electrochemical-based Recovery of O2 from Metabolic CO2

Future long-duration missions will require a sustainable and efficient system capable of yielding a minimum of 75% O2 recovery from metabolic CO2 to achieve self-sufficiency for long space missions beyond Earth's low orbit. A Microfluidic Electrochemical Reactor (MFECR) development effort to electrochemically recover O2 from CO2 is underway at NASA Marshall Space Flight Center (MSFC) to increase current O2 recovery efficiency and reduce air revitalization (AR) system complexity at the International Space Station (ISS) habitat and future long missions. The authors have developed and deployed a comprehensive 3D multiphysics model that thoroughly replicates the actual configuration and fluid/material domains of the MFECR. This model's electrochemical physics consists of multicomponent-multiphase electrochemical-driven reactions leading to CO2 conversion to C2H4 and CO along with the formation of H2 on the cathode in parallel with the generation of O2 and H2O on the anode. This electrochemical model is coupled with all the physics phenomena involved in the process, including but not limited to fluid and non-ideal mass transfer of reactant and product species in free/porous media, convective/conduction/radiative heat transfer, and conduction of DC electrical current with Joule heating generation. The model has proved to be an essential optimization tool using the O2 conversion from CO2 as the objective function and the dimensions of three different Engineering Design Unit (EDU) geometry layouts and two inlet process conditions as input variables. The three MFECR geometry layouts include one without serpentine paths (plain) and two with serpentines leading to four and twelve paths, respectively. The two inlet process conditions include CO2 flow rate and temperature. The MFECR's test stand is fully automated and equipped with several inline measurements (flow, pressure, temperature, pH, component concentration) systems on all six MFECR's IO streams, allowing reliable experimental validation of the model and parametric determination of all electrochemical reactions.