3D numerical investigations of the effect of fill factor on dispersive and distributive mixing of rubber under non‐isothermal conditions

Abstract

Three-dimensional, non-isothermal, transient computational fluid dynamics simulations are conducted for rubber mixing with a set of two-wing rotors in a partially filled chamber. The main objective is to analyze the effect of different fill factors of rubber on dispersive and distributive mixing characteristics by simulating 15 revolutions of the rotors rotating at 20 rpm. 60%, 70%, 75%, and 80% are the four different fill factors chosen for the study. An Eulerian multiphase model is employed to simulate two different phases, rubber and air, and the volume of fluid technique is used to calculate the free surface between two phases, in addition to the continuity, momentum and Energy equations. To characterize non-Newtonian, highly viscous rubber, shear rate and temperature dependent Carreau-Yasuda model has been used. A set of more than 3,600 massless particles are injected after a certain period of time to calculate several quantities in terms of dispersive and distributive mixing. Both the Eulerian and Lagrangian results showed that, fill factors between 70% and 80% presented the most reasonable and efficient mixing scenario, thus exhibiting the best dispersive and distributive mixing characteristics combined. POLYM. ENG. SCI., 59:535-546, 2019.

Numerical Modeling of the Mixing of Highly Viscous Polymer Suspensions in Partially Filled Sigma Blade Mixers

“…The results are fairly similar for all simulations, which indicates that preheating and heating during the process do not have a big influence on the mixing quality after 30 min. The dispersive mixing index is primarily between 0 and 0.5, which is similar to the findings of Ahmed and Chandy [12], who simulated a two-wing rotors mixer. However, the λ mz values are lower than the predictions by Connelly and Kokini [30], who studied a fully filled sigma blade mixer, which indicates that a partially filled mixer seems to have a decreasing effect on how well dispersed the particles will be in the suspension.…”

“…However, when dealing with highly viscous fluids, viscous heating can be present if they are mixed with a certain force. Consequently, this leads to an impact on the energy balance and should therefore only cautiously be ignored, as shown in previous studies [12,26,27].…”

“…One of the pioneers within the field of mixing is Ica Manas-Zlaczower [6][7][8][9][10][11]. Her famous dispersive mixing index from 1992 is still used today [12][13][14][15][16][17], along with her distributive Cluster Distribute Index [12,17,18]. There have not been many alternatives to Zlaczower's dispersive mixing index.…”

“…Heating is an important aspect of mixing, since it can reduce viscosity drastically [12,17,24,25]. The advantage of reducing the viscosity is that it leads to an increased Reynolds Number, which improves mass transfer (i.e., mixing) [25].…”

Simulation Method for Rubber Compounding under Isothermal Partial Filling Conditions

“…In contrast, the calculation efficiency of a 2D model is higher than that of a 3D model. Therefore, some scholars tend to use 2D models for analyzing and calculating [10,11]. However, some scholars tend to use the 3D model for analyzing and calculating because it is closer to the actual working conditions [12,13].…”