Experimental Analysis of Pressure Distribution in an Oval Type Mixer for Polymeric Material

Abstract

In a previous paper, the pressure distribution was theoretically analyzed for the original behavior model in which polymeric material flowed from a wide channel that tapered down into a narrow one, corresponding to a space between the rotor and chamber of an oval type mixer. In this paper, the theoretical analysis was compared with the results of experiments which used low density polythylene in a one rotor mixer. For a non-Newtonian fluid, the numerical solution agreed with experimental results in the case of a complete melt. However, agreement between theory and experimental results during the initial period of mixing was poor. The experiments showed that a layer of unmelted material remained on the rotor surface at the front face of the rotor. This gradually dispersed into the melt so that both solid and liquid phases coexisted within the flowing material. The original behavior model was modified to include the correct viscosity of the fluid with coexisting solid and liquid phases, as well as the correct angle between the chamber and the boundary of the unmelted layer. After the new behavior model was applied, analysis showed that the pressure distribution for the non-Newtonian fluid agreed more closely with the experimental results during the initial period of mixing. Furthermore, the experiments confirmed theoretical predictions that maximum pressure occurs at the front face of the rotor.