Laminar flow and heat transfer in an internally-cooled hexagonal parallel-plate membrane channel (IHPMC)

A internally-cooled hexagonal parallel-plate membrane contactor has been proposed and employed for liquid desiccant air dehumidification, which contains a series of internally-cooled hexagonal parallel-plate membrane channels (IHPMC) for the liquid desiccant stream. Several cooling tubes are installed in the solution channel to take away the absorption heat swiftly. The friction factors and heat transfer coefficients in the complex IHPMC are necessary for the structural design and energy analysis. This study will be focused on the influences of the channel structural parameters on the product of mean friction factors and Reynolds number (fRe)m and Nusselt numbers (Num) in the IHPMC, instead of on the coupled heat and mass transports. 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)m and Nusselt numbers (Num) are calculated and analyzed. Influences of the tube numbers (N), tube outer diameters (do), tube distributions, Reynolds number (Re), and tube shapes on the (fRe)m and Num are studied. It can be found that when the do is equal to 0.002 m, the (fRe)m rises with an increase in the N, while the Num decrease with the N increasing. When the N is fixed as 3, the (fRe)m increase with the do increasing, and the Num decrease with the do increasing. The results are useful for the performance evaluation, structural design of the membrane contactors formed by the IHPMC used for liquid desiccant air dehumidification.