What is Residence Time in Polymer Extrusion?

Residence Time:This provide information on how much time each particle of polymer melt spent inside the die cavity before exiting the die. Solver computers the residence time by solving a scalar transport equation using the computed velocities

When there are dead elements in flow domain, when the velocity is very low or any regions from which material cannot escape, this value can become very high. Solver now limit the maximum to 3600s (1 hr), which is very high value for industrial applications. In future release, solver will automatically ignore these dead elements in computation and hence compute maximum residence time value more accurately.

How to review Residence Time results?

  1. Load results and plot Residence Time. Results below show Residence time for a mono-polymer extrusion die.
    1. In this model, maximum residence time is 1283 sec (21 mins) near corners as seen below image.

  2. Now review residence time at exit face to know what is maximum residence time.
    1. Use Callouts function to review residence time values at few critical locations.

  3. From figure above, the maximum value is about 315 sec (5.3 mins).
  4. To locate dead zones in flow domain; you can set max value in legend as 1.5 to 2 times this max residence time (i.e. around 500 for this model).
  5. Move slide bar to hide value below slider level value. You can see regions with high residence times only. Regions visible will be possible dead zones in flow domain of extrusion.