Theoretical derivation and comparative evaluation of mass transfer coefficient modeling in solar distillation systems - The Bowens ratio approach

In the present investigation a group of mass transfer coefficient expressions was derived based on the definition of Bowen's ratio as applied on a properly modified diffusive interface model, under specific assumptions which impose the restrictive conditions for application in solar distillation systems. These conditions determine the validity range of the derived expressions that include Dunkle's mass transfer models, which as it was recently derived by extensive experimental evidence although are sufficiently accurate at ordinary fail at higher operating temperatures. Based on the developed analysis it was found that this is mainly attributed to the full account of partial water vapor pressures and the neglecting of induced flow enhancement phenomena, which decisively influence the mass transfer as the operating temperature increases. It was also derived that the impressive accuracy of the Chilton-Colburn model, which has been experimentally validated at a broad range of operating conditions, is basically attributed to the complete lack of specific restrictive assumptions. These, combined to the proper account of Lewis number for saturated mixtures as well as the appropriate consideration of mass transfer enhancement phenomena at higher operating temperatures, contribute to the development of an accurate mass transfer model of a more universal nature, suitable for application at a broad range of operating conditions.