Design and Ductile Behavior of Torsion Configurations in Material Extrusion to Enhance Plasticizing and Melting

In the present work, the ductile formation mechanism of a newly proposed torsion configuration has been investigated. One of the unique attributes of this paper is the first-time disclosure of the design and fabrication of a novel prototype screw with torsional flow character validating the orthogonal test model experimentally. The torsional spiral flow patterns that occurred in the torsion channel cause a ductile deformation of polymer in the form of a spiral, which in turn enhances the radial convection, achieving an effective mass transfer of material from the top region to the bottom region and vice versa. Furthermore, the characteristic parameters of torsion configuration have a significant influence on the plasticizing and melting capability of polymer. By range analysis and weight matrix analysis, the best factor and level combination was obtained. Results indicated that the aspect ratio of the torsion channel is almost equal to 1, and the plasticizing and melting capability of polymer is optimal. This novel design innovation offers a paradigm shift in the energy-efficient plasticization of polymer compounds.

Study on characteristics of fluid flow and heat transfer in the torsional flow heat exchanger with drop-shaped tube

Adopting enhanced tube is an effective way to enhance the performance of a shell-and-tube heat exchanger. In this paper, a drop-shaped tube with streamlined cross-section was used to enhance heat transfer of the torsional flow heat exchanger. The characteristics of the fluid flow and heat transfer in torsional flow heat exchanger with drop-shaped tube were studied numerically, considering three kinds of axis ratios (a/b=1.5, 1.8, 2) of the tube. The reliability of numerical results was verified through experimental results. The results indicate that the wake size of the streamlined drop-shaped tube is smaller than that of the conventional smooth tube, and the drop-shaped tube reduces the flow dead zone in torsional flow heat exchanger. As the axis ratio of a/b increases, the shell side Nusselt number and comprehensive performance increase, due to enhancement of the turbulence kinetic energy of the transition section. When the axis ratio is 2, the Nusselt number is increased by 12.44-18.99%, and the comprehensiveness is increased by 13.27-19.2%, compared with the torsional flow heat exchanger with the smooth tube. The quantitative analysis of the velocity indicates that the relative magnitude and proportion of transverse velocity components of fluid are important factors affecting the thermal-hydraulic performance of torsional flow heat exchanger.

Consequences of viscous anisotropy in a deforming, two-phase aggregate. Part 1. Governing equations and linearized analysis

In partially molten regions of Earth, rock and magma coexist as a two-phase aggregate in which the solid grains of rock form a viscously deformable framework or matrix. Liquid magma resides within the permeable network of pores between grains. Deviatoric stress causes the distribution of contact area between solid grains to become anisotropic; in turn, this causes anisotropy of the matrix viscosity at the continuum scale. In this two-paper set, we predict the consequences of viscous anisotropy for flow of two-phase aggregates in three configurations: simple shear, Poiseuille, and torsional flow. Part 1 presents the governing equations and an analysis of their linearized form. Part 2 (Katz & Takei, J. Fluid Mech., vol. 734, 2013, pp. 456–485) presents numerical solutions of the full, nonlinear model. In our theory, the anisotropic viscosity tensor couples shear and volumetric components of the matrix stress/strain rate. This coupling, acting over a gradient in shear stress, causes segregation of liquid and solid. Liquid typically migrates toward higher shear stress, but under specific conditions, the opposite can occur. Furthermore, it is known that in a two-phase aggregate with a porosity-weakening viscosity, matrix shear causes porosity perturbations to grow into a banded or sheeted structure. We show that viscous anisotropy reduces the angle between these emergent high-porosity features and the shear plane. Laboratory experiments produce similar, high-porosity features. We hypothesize that the low angle of porosity bands in such experiments is the result of viscous anisotropy. We therefore predict that experiments incorporating a gradient in shear stress will develop sample-wide liquid–solid segregation due to viscous anisotropy.