Air dehumidification by hollow fibre membrane with chilled water for spacecraft applications

Abstract

A novel hydrophobic membrane-based dehumidification technology with chilled water is proposed to substitute the traditional dew point method for humidity control in spacecraft, which fulfils the tough tasks of air/water separation and water reuse under low gravity at the same time. A prototype hydrophobic membrane module was designed and fabricated by packing 853 hollow fibres in the shell-and-tube configuration, which could prevent the leakage of the tube-side chilled water to the air side. Theoretical models concerning conjugated heat and mass transfer have been established for the explanation and prediction of the moisture migration across the membranes. Experiments were conducted to validate the theoretical models and the feasibility of water vapour removal under various operating conditions. Although undesirable dewing occurred on the outer membrane surface due to the slow mass transfer relative to heat transfer across the membranes, it was verified by the water increase in graduated cylinder that some water vapour actually transferred through the membrane pores under partial pressure difference. A maximum net dehumidification rate (excluding dewing) of 45 g/h has been achieved by the experiment.