Flow modeling for conveying sections in a co-rotating twin-screw extruder based on energy dissipation rate for continuous mixing of lithium-ion battery slurries

In the present work, we propose a new modeling scheme for flows of non-Newtonian fluids in the fully filled narrow-pitched conveying section in a co-rotating twin screw extruder, emphasizing the application to viscoplastic lithium-ion battery slurries for electrode manufacturing. A predictive tool for the relationship between flow rate, screw speed, and pressure build-up was presented for flows with a general class of inelastic non-Newtonian fluids. By introducing the effective viscosity and effective shear rate based on the energy dissipation rate, we showed that the conventional relationship between throughput number and pressure number for various non-Newtonian fluids collapse into a single master curve of a Newtonian fluid, from which the predictive relationship between flow rate, screw speed, and pressure build-up was established. The method was validated numerically with power-law fluids, a Carreau fluid, and a Herschel-Bulkley fluid (anode slurries) for a narrow-pitched conveying element module.