Quasi-counter flow parallel-plate membrane contactors (QCPMC) for liquid desiccant air dehumidification: Conjugate heat and mass transfer

A quasi-counter flow parallel-plate membrane contactor (QCPMC) has been applied for liquid desiccant air dehumidification. The air stream flows straightly in the rectangular channels, while the liquid desiccant (salt solution) flows in the side in and side out channels. The concept is similar to an air-to-liquid heat and mass exchanger where the air and the solution streams are separated by the selectively permeable membranes. The air is dehumidified by the water vapor transport from the air stream across the membranes into the solution side, while the solution is prevented from permeating through the membranes. A three-dimensional mathematical model describing the heat and mass transports in the membrane contactor is built based on an element including a piece of the membrane, half of the air channel, and half of the solution channel. The momentum, energy and mass conservation equations are simultaneously solved. The average product of friction factor and Reynolds number (fRe)m, Nusselt number (Num) and Sherwood number (Shm) under the conjugate heat and mass transfer boundary conditions are then obtained. Effects of the length-height ratios (x0/H), length-width ratios (x0/y0), entry ratios (xin/x0), and flow arrangements (quasi-counter, counter, and cross-flow) on the (fRe)m, Num and Shm are analyzed. It can be found that the length-height ratios (x0/H) have relatively more obvious influences on these basic values of the QCPMC.