The simulation we describe hereafter is coming from a case defined at the Minho University (Protugal). This exeperiment and the first simulations have been defined in a scientific publication⁽¹⁾ of O. S. Carneiro, J. A. Covas and B. Vergnes.

The first simulation has been realised in 2000. Today, this case has been rebuilt with Ludovic V5.0 with the following data :

The Equipment : Leistritz LSM 30/34 twin screw extruder (with pressure and temperature sensors)

The Product : Polypropylen Homopolymer HB121J - Borealis

The Process Conditions :
Homogeneous regulation temperature : 210°C
FleedRate : 12kg/h
Screw Rotation Speed : 150Rpm

Several pressure and temperature measures allow the comparison between experimental and simulation results.

Real profile of the used Leistritz twin screw. The points 1 to 6 represent the pressure and temperature sensors.
Journal of Applied Polymers Science, Vol. 78, 1419-1430 (2000)
^©2000 John Wiley & Sons, Inc.

The used screw profile holds the following elements :

(A negative pitch indicates a left handed elements. KD-30 means a left handed kneading block with a staggering angle of 30°)

The used Product is defined as hereafter :

A Carreau-Yasuda law has been used for this kind of Product.

Considering the thermal conditions, a heat transfer coefficient has been used:
Between the product and the barrel : h= 1500W/m²/°C
Between the product and the die : h= 1500W/M²/°C

The different screw elements have been defined regarding the previous characteristics. The modelling of the screw in Ludovic is presented hereafter :

Product has been defined with the previous product characteristics (mechanical properties and viscosity law).

The given process conditions have been applied : feed rate 12kg/h and screw rotation speed 150Rpm.

To be as closed as possible to the experimental configuration, we have planned to use a computed Melt Point. It means that Ludovic will compute the point of melt of the product during the process. This grants a better accuracy of Results.

The computation has then been launched.

After a first simulation, results present the tendances of the measures.

The left y-axis represents the temperature (orange). The measurements are represented by orange crosses.

The right y-axis represents the pressure (blue). The measurements are represented by blue crosses.

After a first simulation, the forecasted tendances are pretty good, even if they are overrated : the pressure and temperature increases are well underlined when the product flows through the kneading elements (in red on the screw profile).

On the whole, these results can be improved. A second step of optimization can be done to get more accurate results.

Carneiro O.S., Covas J.A. and Vergnes B., Expermiental and theoretical study of polymer flow in a co-rotating twin screw extruder, Journal of Applied Polymer Science, Vol.78, pp 1419-1430 (2000)