Experimental and theoretical analysis of air humidification/dehumidification processes using hydrophobic capillary contactors

This paper deals with an experimental and theoretical investigation of air humidification/dehumidification processes carried out in a hollow-fibre membrane contactor. The cross-flow contactor consists of a 1.2 m2 total membrane surface of hollow polypropylene capillaries arranged in a staggered array and has a mass transfer area per unit volume of 593 m2/m3. The heat and vapour mass transfer between the liquid phase (water and LiCl saturated solution) and the process air is analysed. During the humidification process, experiments were carried out using three different mass flow rates of water (19, 35, 54 kg/h), while two different mass flow rates of LiCl saturated solution (25, 41 kg/h) were used for air dehumidification. Air flow rates ranging from 30 to 80 m3/h were considered. Variations in the relative humidity of the air and in the temperatures of the air and liquid were measured. Experiments show a high mass transfer efficiency for both humidification and dehumidification. Furthermore, a numerical model to predict heat and mass transfer through the contactor has been developed. Experimental results are in good agreement with theoretical predictions.