Simulation and Experimental Investigation of the Two-Phase Flow Field in Jet Loop Reactors

Abstract

D i p l . -I n g . R o b e r t A n g s t D i p l . -I n g . P a t r i c k M i e r P r o f . D r . -I n g . M a t t h i a s K r a u m eIn this contribution the results of Computational Fluid Dynamics (CFD) simulations of the turbulent two-phase flow field and the particle distribution in a laboratory-scale jet loop reactor are presented. Furthermore these results were validated by flow velocity measurements carried out using Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). The comparison of numerical and experimental results allows the judgment and the further development of existing simulation models. It can be concluded that the accuracy of the simulation results is decisively influenced by the description of momentum transfer between the turbulent jet and the surrounding fluid as well as the description of the inter-phase momentum transfer. This paper deals with the local residence time distributions (RTD) in an intermeshing corotating twin screw extruder and shows their interest. The RTDs were measured in three zones of the extruder and tracer was injected at different locations. Optical fiber probes are used in order to obtain real-time measurements of fluorescence radiation during extrusion of polyethylene HDPE and fluorescent particles of anthracene. First, experiments were carried out to measure local residence time distributions in different processing conditions and to determine the quality of mixing thanks to the specific throughput. Then, the convolution theory was verified by comparing the convolution of local RTDs functions to the overall RTD. Finally, a predictive RTD model for twin screw elements based on the flow analysis of the individual screw zones and their statistical superpositions was developed.