Analysis of boundary layer and solute transport in osmotic evaporation

Abstract

AbstractThe osmotic evaporation process (OE) is based on the transfer of solvent from a dilute solution to be concentrated to an extraction medium (for example, a highly concentrated brine) separated by a macroporous hydrophobic membrane. Mass transfer takes place in the gas phase through the membrane pores under the influence of the water activity gradient. The OE process has been analyzed before in experiments by Courel et al. in 2000 and models by Romero et al. in 2001. These previous studies take into account the effect of structural membrane parameters and working conditions of water flux performance. An algorithm has been developed to solve the system constituted of the mass‐ and heat‐transfer equations. In order to validate it more easily, the simulation was conducted for the results of pure water evaporation. This provides a lot of interesting information on transfer resistances, temperature, and concentration profiles, as well as the prediction of water flows. A work that is the logical continuation of these previous studies is proposed. First, it aims at explaining the influence of the concentration polarization that develops at the solution–membrane interface when the concentration is applied to a sucrose solution. The transfer of very dilute volatile compounds from the sweetened solution is also analyzed with a view to understanding the mechanism that controls the loss of aroma compounds during the concentration of fruit juices.