Advection diffusion model for gas transport within a packed bed of JSC-1A regolith simulant

Abstract

The advection diffusion model was evaluated for gas transport within a packed bed of lunar JSC-1A regolith simulant at low to medium total pressures over three flow regimes: (1) the slip flow (2) transition and (3) Knudsen regimes. These regimes are pertinent to the design of H2O extraction devices for in-situ resource utilization, sampling missions, and surface science. Experiments were conducted over a range of average pressures of 100 to 25,000 Pa, corresponding to Knudsen numbers between 0.01 and 100 at ambient temperature with Ar and N2. Non-condensing gases were evaluated to isolate key flow properties as a first step towards evaluating more complex H2O flows. Experimental results were coupled to physical models, and key properties were evaluated to assess the model fit. The experimental results in the transition regime followed the expected behavior based on similar work for microchannel flow and showed that advection is not negligible for transition regime flows. The advection diffusion model in the transition regime fit the results for Knudsen numbers less than unity, and showed the need to further develop gas slip models for Knudsen numbers greater than unity. Parameters necessary to define were the porosity, tortuosity, wall diameter of the regolith medium, and the gas slip parameter was key in determining the gas-specific transport rate.