Thin film theory and boundary layer theory, an approach for analysing heat and mass transfer in spacer-filled Direct Contact Membrane Distillation

Heat and mass transfer in spacer-filled direct contact membrane distillation were experimentally investigated and explained in more detail based on the combination of the thin film theory and boundary layer theory.Experimental results were used to calculate mass transfer coefficient through the boundary layer instead of existing Sherwood number correlations or modeling results.Consequently, the change of direct contact membrane distillation (DCMD) performance in terms of mass fluxes, temperature polarization coefficient (TPC), and concentration polarization coefficient (CPC) could be analyzed more clearly through the fluctuation of mass transfer coefficient through the boundary layer, and boundary layer thickness.Moreover, the results also revealed that the effect of membrane pore size on the mass transfer coefficient through the boundary layer, boundary layer thickness, and internal heat transfer coefficient was insignificant.In contrast, membrane pore size considerably influenced the membrane permeability coefficient, TPC, and CPC.