TECHNOLOGY | PROCESS MODELLING


research consortium developed the model of assisted microwave energy sourcing and SCC integrated it into the Ludovic software. Ratte says the standard reactive extrusion model is already part of the Ludovic license; the Micro-Wave model will be available commercially later this year.


Figure 1: Ludovic software can be used to perform a design of experiments for optimising throughput on a twin-screw extruder. The green area indicates the region where the targeted specific mechanical energy (SME) is maintained (green axis) with changing throughput (blue axis) and rotation speed (red axis). Throughput can be increased from the base case (yellow dot) to a higher throughput (pink dot). Source: Sciences Computers Consultants


blocks and turbine mixing elements—into its Ludovic software. Simulation can also be helpful when using


twin-screw extruders for reactive extrusion process- ing. Reactive extrusion depends on both tempera- ture and time in the extruder for the reaction to take place. A relatively new development that aims to


improve the process and possibly make heating more “eco-friendly” is the use of additional energy sources, such as microwaves or ultrasound. A microwave heating source placed on the extruder can concentrate heat in a localised area to help initiate reactive extrusion, says Ratte.


Microwave modelling A paper published last year detailed SCC’s work with researchers from Cranfield University in the UK and Fraunhofer-ICT in Germany to model the reaction kinetics of microwave-energy assisted synthesis of polylactic acid (PLA) via continuous reactive extrusion. The EU-funded InnoREX


Saving time on 3D 3D simulations use finite element method (FEM) or computational fluid dynamics (CFD) to accurately model what is happening inside the machine, but these are time consuming to compute. One-dimen- sional (1D) simulations are less detailed approxima- tions but require less computing time. Using 3D simulation results as input data for 1D models can provide a good compromise between accuracy and computing time. Paderborn University’s KTP (Kunststoffechnik


Paderborn) Plastics Technology Institute in Ger- many uses Extrud3d, a CFD 3D solver, for detailed inputs to its 1D SIGMA modeling software. Ex- trud3d was developed by the Technical University Dortmund and subsequently commercialised by IANUS Simulation, a 2006 spin-off of the Univer- sity Dortmund. This year, KTP will automate the data exchange between Extrud3d and SIGMA, creating the user-friendly SIGMA3D. “The CFD model accurately describes up to


three fully filled screw elements in one calculation. It can be used for isothermal and non-isothermal calculations of shear-thinning polymer com- pounds,” says Frederik Sporkmann, SIGMA project manager at KTP. “For example, if you have two kneading blocks with a conveying element between, you might want to know how high the shear rate is in the kneading blocks. The 1D model doesn’t calculate such local details accurately, but the 3D model can [Figure 2]. The 3D data can be used to identify flow character- istics such as dead zones or wall slipping and further improve the 1D analysis of the whole process [Figure 3]. We can simulate materials with low to high viscosity, within a practical range of the process parameters that are commonly used in the


Figure 2: Extrud3d CFD modelling software can provide a detailed analysis of data (such as viscosity, pressure and velocity) in a localised area


32 COMPOUNDING WORLD | March 2018


Source: Kunststoffechnik Paderborn/IANUS Simulation www.compoundingworld.com


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