Simulation Study of Waste Heat Recovery from Oily Wastewater Outside Smooth and Rough Elliptical Tubes

The technique of falling film vaporization is frequently employed in petroleum refining, pharmaceutical production, and thermal energy recovery due to its advantages of excellent evaporation efficiency, energy conservation, and reduced usage. This research seeks to strengthen the evaporator's structural design and thus enhance the waste heat utilization efficiency of oily wastewater, thereby reducing the cost and energy consumption of wastewater treatment. In this study, for the purpose of analyzing the flow of oil-bearing wastewater outside of smooth and rough elliptical tubes, a numerical model based on the volume of fluid (VOF) approach is developed, and the simulation results of smooth tubes are verified with experimental data. By comparing the kinetic and heat transmission properties between the two structures, some computational results are achieved: (1) More so than the smooth elliptical tube, according to the simulation results, the wastewater outside the rough elliptical tube has a greater heat transmission efficiency; (2) The primary cause of the rough structure's positive impact on heat transmission efficiency is the enhancement of the liquid film disturbance caused by the vortex cluster and reflux phenomena near the wall surface; (3) After the steady flow outside the rough tube, the liquid film displayed a cyclic fluctuation pattern.