Parameters affecting the accuracy of Dunkle's model of mass transfer phenomenon at elevated temperatures

• Mass transfer modeling accuracy in solar distillation systems.
• Restrictive conditions for use of Dunkle's and Chilton–Colburn mass transfer models.
• Derivation of Dunkle's and Chilton–Colburn models based on Bowen's ratio.
• The importance of parameters affecting mass transfer modeling at higher temperatures.

The accurate evaluation of combined transport processes is an issue of vital importance in solar distillation systems. The amount of condensed water vapor, being determined by the energy exchange between the brine and condensing surface, depends on both diffusion and bulk mass transport owing to natural convection phenomena occurring within the specific enclosed space geometry of any distillation unit. In the present investigation, the parameters affecting the modeling accuracy which determine the limitations under which the broadly established Dunkle's model is applicable are being investigated, comparably to the respective accuracy of the recently proposed Chilton–Colburn analogy model. The developed analysis allowed the investigation of the modeling deficiencies highlighting the reasons of degraded accuracy of the Dunkle's mass transfer modeling at elevated temperatures typically higher than about 55 °C, something that was recently indicated by comparative investigations based on extensive experimental evidence. It was found that this was mainly attributed to the omission of parameters which properly define the significant influence of mass transfer enhancement phenomena owing to the induced flow at higher operating temperatures, at which also the proper consideration of transport properties and Lewis number for the saturated mixture become factors of growing importance.