Heat and mass transfer enhancement in a cross-flow elliptical hollow fiber membrane contactor used for liquid desiccant air dehumidification

• An elliptical hollow fiber membrane contactor (EHFMC) is employed for liquid desiccant air dehumidification.
• Friction factor, Nusselt and Sherwood numbers in the EHFMC are obtained.
• The membrane surface boundary conditions can be considered as uniform heat flux condition.
• The heat and mass transfer enhancement is more obvious with the semiaxis ratios (b/a) decreasing.

To improve the performances of a hollow fiber membrane contactor (HFMC) employed for liquid desiccant air dehumidification, an elliptical hollow fiber membrane contactor (EHFMC) is proposed. The contactor is assembled by a collection of elliptical hollow fibers populated in a shell. The liquid desiccant and the processing air streams flow inside and across the elliptical fibers, respectively. They are in a cross-flow configuration. The momentum and the conjugate heat and mass transports in the EHFMC are investigated based on Happel's free surface model. In this approach, a single elliptical fiber, an air stream across the fiber, and a liquid desiccant stream inside the fiber are selected as the calculating element. The air stream in the element is encompassed by a hypothetical outer free surface with an elliptical shape. The equations governing the momentum, heat and mass transports in the air and the solution streams are established and solved together with the conjugate heat and mass transfer boundary conditions. The fundamental data of the friction factor, Nusselt and Sherwood numbers in the element are then numerically calculated, experimentally validated, and analyzed. These basic data are compared with those obtained in the HFMC.