For long-duration space missions, compact and efficient life support systems allowing human survivability in outer space are required. Existing carbon dioxide removal assemblies employing sorption beds packed with desiccant beads show poor thermal transport characteristics during the regeneration process. 3D-printed zeolite lattice structures are considered a potential replacement for the current desiccant-packed bed systems due to their improved thermal transport characteristics. Here, a detailed modeling is conducted to study underlying heat and mass transport mechanisms governing the regeneration process of 3D-printed zeolite lattice structures. The simulation results allow the optimization of zeolite lattice geometry, heater spacing, and material feedstock thermal conductivity, thereby reducing the size, weight, and power (SWaP) of the carbon dioxide removal assembly. It was found that both heat and mass transfer play critical roles in the regeneration process in contrast to the adsorption process where mass transfer plays a larger role. At large zeolite rod diameters, the surface-area-to-volume ratio of the zeolite structure decreases, which impedes the regeneration mass transfer rate. However, a large rod diameter increases the thermal conductance, thereby promoting the heat transfer process. Equally important is the thermal capacity of the zeolite lattice structure, which increases at large rod diameters. Therefore, there exists an intermediate zeolite rod diameter at which the surface-area-to-volume ratio, the thermal conductance, and the thermal capacitance of 3D-printed zeolite lattice structures are balanced for an optimum carbon dioxide regeneration process.
Agata et al. (Sun,) studied this question.