An Effectiveness–Number of Transfer Units Relationship for Evaporators With Non negligible Boiling Point Elevation Increases

Abstract

An effectiveness number of transfer units (خµâ€“NTU) model is developed for use in evaporators where the evaporating stream: (1) comprises a volatile solvent and nonvolatile solute(s) and (2) undergoes a significant, but linear change in boiling point elevation (BPE) with increasing solute molality. The model is applicable to evaporators driven by an isothermal stream (e.g., steamdriven or refrigerantdriven) in parallel flow, counterflow, and crossflow configurations where the evaporating stream is mixed. The model is of use in a variety of process engineering applications as well as the sizing and rating of evaporators in highsalinity desalination systems.