Dynamics of Gas Evacuation from a Honeycomb Structure Having Common Wall Perforations

A model has been developed to provide insight regarding the time to evacuate gas from a sealed structure consisting of elongated hexagonal cells for which the common walls share a relatively small pinhole. Gas flow from a single cell to a vacuum environment, and then between two connected cells, is first considered. The analysis is then applied to a linear string of attached cells, where the pressure drop from the center cell through the edge cell as a function of time and number of intermediate cells is evaluated. Both adiabatic and isothermal conditions were investigated, with the latter resulting in faster drain times. A scaling relationship of the pressure drop between time and the number of cells was found and used to extend themodel to themore complicated, two-dimensional hexagonal array problem. Considering an array based on a typical common bulkhead geometry, and applying the isothermal condition, a best-case evacuation time for argon was predicted.