A model is developed for the design of the devolatilization section in an extruder, which is optimized with respect to foam growth and process parameters. The previously developed bimodal/film model for polymer devolatilization is used to design L-c, the distance from the melt seal to the vacuum port for completion of foaming and breakup in the extruder. The model requires one free parameter, the number of stripper bubbles as a function of important process parameters. A statistical regression method and a backpropagation neural network are used to develop the correlations. The developed correlation along with the bimodal/film model is applied to design a distance, L-c, prior to the vacuum port for completion of foaming and breakup in an extruder. Polyethylene/acrylic acid devolatilization in a 28-mm co-rotating twin-screw extruder is used as a case study for model demonstration.