Heat and mass transfer deteriorations in an elliptical hollow fiber membrane tube bank for liquid desiccant air dehumidification

Abstract

A hollow fiber membrane tube bank (HFMTB) is commonly used for liquid desiccant air dehumidification to prevent small liquid desiccant droplets from escaping to the processing air. Due to the extrusions during the fabrication process, cross-sectional shapes of the circular hollow fibers are easily changed to elliptical ones. To know the effects of the shape changes of the fibers, the conjugate heat and mass transfer in an elliptical hollow fiber membrane tube bank (EHFMTB) employed for liquid desiccant air dehumidification is investigated. The liquid desiccant flows inside the fibers, while the air flows in the shell side in a counter flow arrangement. In the tube bank, a typical unit cell consisting of a single fiber, the desiccant flowing inside the fiber and the air stream flowing outside the fiber, is considered. The air stream outside the fiber has an outer free surface. The equations governing the fluid flow and heat mass transfer in the two streams are solved together with the conjugate heat and mass transfer boundary conditions. The local and average Nusselt and Sherwood numbers in the unit cell are then obtained and experimentally validated. It is found that heat and mass transfer are substantially deteriorated in the EHFMTB.