Experimental Studies of Load-Displacement Behavior of Water Processing Granular Activated Alumina Beds for Space Life Support Systems

Abstract

Long-term human missions to space need advanced life support systems to generate and recycle critical elements like oxygen and water. The water processing assembly aboard the Space Station makes use of granular packed beds to process/recycle water. This article presents results from an experimental study of dry granular activated alumina (AA) packed beds that have application for water processing. Laboratory tests performed included particle size distribution, direct shear, axial loading/unloading, and friction mobilization tests. It is found that internal friction of the media increases with increasing initial compaction. The interface friction coeffi cient between AA and the housing cylinder wall shows modest change with increase in compaction. The load-displacement behavior of the full-scale bed is nonlinear for low compaction but becomes linear for high compacted media. The axial displacement at the loading end of the bed increases with decrease in initial compaction. The amount of fi nes generated in the media increases with decrease in initial compaction. Friction mobilizing force between AA and the housing cylinder is found to be signifi cant and increases with initial compaction and bed length of the media.

Experimental determination of friction coefficient and mobilization force for a laterally confined granular column

“…The granular material column is held in vertical equilibrium only by the friction forces acting along the tube wall, which equilibrate all loads including the weight of the granular material and a possible surcharge applied at the top of the granular column. This situation can be found in various engineering applications, for example: in caissons construction and pile driving [1], in the design of silos and hoppers [2], or in space life support systems for water processing where granular material contained in a cylinder is compressed by a spring [3][4][5][6]. When a piston with a gradually increasing load is applied to the top (see Fig.…”

“…The development of the experimental set-ups and procedures has been motivated by a research project on the stress-strain behaviour of granular material confined in a rigid cylinder [3][4][5][6][7], whose key question was the accurate prediction of the top surcharge that guarantees the proper compaction for the entire length of the granular column. The answer to that problem is in fact In contrast to conventional methods [8], here emphasis is placed upon the development of experimental set-ups and procedures for the in-situ determination of the Coulomb's friction coefficient and the mobilization force.…”