Laminar flow and heat transfer in a quasi-counter flow parallel-plate membrane channel in the solution side with cooling tubes

An internally-cooled parallel-plate membrane contactor has been proposed, designed, and used for liquid desiccant air dehumidification. It is comprised of a series of side in and out parallel-plate membrane channels (QCPMC). The processing air and the liquid desiccant (solution) streams are separated by the membranes. Cooling tubes are installed in the solution channel to take away the absorption heat. The friction factors and heat transfer coefficients in the complex QCPMC with the cooling tubes in the solution side (QCPMCC) are necessary for the structural design and energy analysis. Therefore the laminar flow and heat transfer in the solution channel are studied based on a unit cell containing the sandwiched domain outside the cooling tubes between two neighboring membranes. The momentum and thermal transport governing equations are built up together with a uniform wall temperature boundary condition and solved by a finite volume approach. The mean (fRe) and Nusselt numbers (Num) are then calculated. Influences of the Reynolds numbers (Re), tube number (Ntube), tube outer diameters (douter), tube arrangements, and connection types of tubes on the (fRe)m and Num are analyzed. It can be found that when douter = 0.003 m, the (fRe)m rises with an increase in the Ntube. However the Num decrease with the Ntube increasing. When Ntube = 4, the (fRe)m rise with an increase in the douter. However the larger the douter are, the smaller the Num are.