A Vacuum Dephlegmation Model for Ethanol–Water Permeate Vapor Concentration during the Pervaporation Process Considering Heat-Synergistic Mass Transfer

A heat-synergistic mass transfer model for describing the ethanol–water permeate vapor dephlegmation performance in a vacuum condensation dephlegmator (VCD) during the pervaporation process was built based on mass conservation, heat conservation, and vapor–liquid phase equilibrium. The model predicted the flow rate of the condensate Mc and outlet vapor MN, and the ethanol concentration in outlet vapor yN, with low errors of 2.43%, 3.88%, and 4.80%, respectively. When the total heat transfer coefficient K increased from 100 W m–2 °C–1 to 934.2 W m–2 °C–1, the ethanol concentration in condensate xc rose from 4.15 to 12.79 wt %, while the ethanol concentration in outlet vapor yN increased from 33.02 to 81.80 wt %. In contrast, the proportion of the outlet vapor to the total vapor decreased from 89.54% to 24.95%, and the ratio of ethanol vapor at the outlet to the total ethanol vapor dropped from 98.55% to 68.40%. Trends in Mc, MN, yN, and xc with variations in total heat transfer area A aligned with those observed for changes in K. Trends in Mc, MN, yN, and xc with variations in inlet cooling water temperature t0 and inlet vapor flow rate M0 were opposite to that in K. Ethanol concentration in inlet vapor y0 primarily affected the outlet ethanol concentration, with a minimal impact on recovery rates. The model could accurately predict dephlegmation performance in a pilot-scale VCD, showing its promising feasibility in practical application.