Coupling effects among viscosity, viscous dissipation and convective heat transfer in the microscale flow of polymer melt

Abstract

The coupling effects among viscosity, viscous dissipation, and convective heat transfer during the polymer melt micro-molding process, influenced by microscale effects, notably impacted the melt's flow characteristics. The scarcity of theoretical exploration into these coupling effects has hindered the evolution of micro-molding. This research initially established the heat transfer coefficient equation at the microscale via experimental approaches, and by integrating multiphysics coupling theories, established a coupled mathematical model encompassing viscosity, viscous dissipation and convective heat transfer at the microscale. Then we computed and analyzed the melt flow characteristics within microchannels of varying characteristic dimensions and validated the temperature variations of the melt along the flow direction through experiments. The results showed that considering coupling effects resulted in a temperature rise along the flow direction that closely matched experimental data, with discrepancies below 0.5 °C, whereas ignoring these effects led to a maximum deviation of up to 2.4 °C. Analysis of velocity, viscosity, and viscous dissipation across radial section revealed that the discrepancies between ignoring and considering coupling escalated with decreasing dimensions. The maximum deviations for velocity, viscosity, and viscous dissipation in PMMA(polymethyl methacrylate) were 19.47 %, 10.71 %, and 39.28 %, respectively. These results emphasized the necessity of considering coupling effects when polymer melt micro-molding.