LOAD AND DEFLECTION CHARACTERISTICS OF WATER DE-IONIZING MEDIUM FOR SPACE APPLICATIONS

摘要

One of the most critical components in the oxygen generation assembly for long term human habitation system in space is the de-ionizing (DI) bed - a packed bed of ion-exchange resin beads - that purifies water by removing ions (dissolved salts and organic impurities) from reclaimed water. The DI bed shrinks during the course of its operation. For the bed to work satisfactorily, it is required that the bed is kept compressed and this is done with the aid of a compressed spring mechanism placed at one end. In this study, an experimental investigation is carried out in a DI bed material of Amberlite IRN-78 ion exchange resin to determine its load-deflection characteristics. Results are also presented for the factor to relate applied axial normal stress to induced lateral normal stress, shear angle, and apparent cohesion of DI bed material medium, and the load-deflection characteristics and most probable crushing force of individual ion-exchange resin beads. It is observed that the applied axial normal stress and the induced lateral normal stress at the inner wall surface have a linear relationship. The results also show that the ion-exchange material medium exhibits time dependent behavior, namely creep and stress reduction, possibly through particle re-arrangement.