Study On Heat And Mass Transfer Of Non-Newtonian Fluid In Screw Plasticizing System

Seeking effective methods to improve the plasticizing quality has always been the core of plastic processing direction research.As the most important part of extrusion processing equipment,screw has the most direct influence on the plasticizing process of plastics,and finally affects the properties of products.The research on screw has been an important research direction to improve the plasticizing quality and product quality.How to provide direction for further screw innovative design and further optimize screw structure was an important research topic in this direction.In this paper,a new type of torsion element proposed by our laboratory team was taken as the research object,focusing on the influence of torsion element on the flow behavior of melt in the screw groove and the heat transfer characteristics of the plasticizing system in the process of polymer plasticization.The main research contents were as follows:(1)The visual experimental method was used to simulate the observe the flow behavior of the melt in the screw conveying section,especially the flow state in the screw groove of the new torsion element.The results show that the structure of the torsion element was unique,and the melt in the screw groove could be spirally flowed,which promoted the mass transfer in the depth direction of the groove and was beneficial to the mass transfer between the top and bottom of the groove.(2)Using the on-line data acquisition system of the extruder developed by ourselves,the temperature and pressure distribution along the axial direction of the traditional three-section screw and the new building block screw with the new field cooperation element were measured respectively under different processing conditions.The mean value of the temperature and pressure in the metering section of the screw and the melt temperature and pressure fluctuation in the head of the screw were analyzed,and the heat transfer coefficient in the homogenization section was calculated.Through comparison,an optimal combined configuration of the torsion element was obtained.The results show that the quality of the melt was improved after the torsion element was added.It was found that the configuration of the six torsion elements arranged side by side was the optimal one of the four configurations used in the experiment.(3)On the basis of the existing new model of field cooperative element,two kinds of changes were made.Numerical simulation was used to compare the effects of three kinds of elements on the velocity field of polypropylene during the plasticizing process.The analysis results showed that the configuration of the helical element forming an angle with the helical tilting of the torsion element was improved both in radial velocity distribution and shear rate distribution.The configuration in which the helical element of the torsion element was inclined at an angle with the axial direction was improved in the mixing effect.A further idea was provided for twisting components.