Effect of viscous dissipation on the temperature of the polymer during injection molding filling

Abstract

During injection molding, viscous dissipation changes the temperature distribution by playing the role of an energy source, which affects heat transfer rates. Understanding the effect of the viscous dissipation assists the designing of the cooling system in injection molding process. In this article, the effect of the viscous dissipation on the temperature distribution throughout a rectangular channel for different polymers at different inlet velocities and temperatures is studied. A cross type rheological model depending on the temperature and pressure is assumed for polymer materials polystyrene (PS) and polypropylene (PP). The evolution of the flow velocity inside the channel is presented. The quantity of heat added due to viscous dissipation to the polymer is also calculated up to different positions through the channel. A numerical finite volume code for the simulation of polymer melt flow in a channel is used and a validation of this numerical code is presented.

Effect of viscous dissipation on natural convection flow between vertical parallel plates with time-periodic boundary conditions

“…In a related work [23], two different perturbation expansions were used to study the fully developed laminar mixed convection in an inclined channel, and it was reported that the presence of viscous dissipation leads to a sharp dependence of the dimensionless pressure drop coefficient and the Nusselt number on the Grashof number. Further contributions on the effects of viscous dissipation were made by the authors of [24][25][26][27][28][29][30]. The objective of this paper is to investigate the flow behavior of fluid in vertical channel when the convection is induced by the periodic heating of the plates and the effect of viscous dissipation is considered.…”

Computational Modeling of the Effects of Viscous Dissipation on Polymer Melt Flow Behavior During Injection Molding Process in Plane Channels

“…Energy equation in conservation form including the viscous heating term can be written as [or = v-(/:vr)-|^r(v-v) + <i ) (6) where k is the thermal conductivity and Cp is the specific heat, xj and ß are the compressibility and dilation coefficients, respectively, and given as 1 fdu\ (7) The last term in Eq. (6) is viscous dissipation which is the function of viscosity and shear rate and can be given in the following form: …”

“…The heat generated by viscous friction leads to a local temperature increase especially in the high shear layer regions in the vicinity of the wall surfaces which in turn reduces the viscosity of the polymer melt flow in these regions and this may significantly change the local flow and heat transfer characteristics of the polymer melt flow during the manufacturing process. Therefore, studying of viscous dissipation effects on the polymer melt flow in the analytical [2-5] and numerical [6][7][8][9][10] investigations has received a great attention in recent years for the optimization of existing manufacturing processes in addition to alternative research studies [11,12] for analyzing effects of nanoparticles and processing conditions on the development of local microstructures under thermal and deformation fields experienced in injection molding processes. The recent experimental studies [13,14] also emphasize the importance of the viscous dissipation effects in high viscous flows or in presence of high gradients in velocity distributions for polymer process applications of micro channels.…”

“…The recent numerical studies [6][7][8][9][10], on the other hand, present more complete simulation solutions for viscous dissipation effects on thermodynamic transport characteristics of polymer melt flow in mold and cavities. These numerical studies/efforts aim at improving existing numerical modeling capabilities for a full understanding of the polymer process dynamics with viscous heating.…”

A numerical study of solidification and viscous dissipation effects on polymer melt flow in plane channels

“…Zdanski and Vaz Jr [16,17] and Hassan et al [18] independently simulated viscous dissipation effects on hydrodynamically developed, but thermally developing melt flows in plane channels using simplified solutions of governing flow equations. Their results concluded that high viscous dissipation would associate with high velocities and its effect would be important for long channels exposed to low injection polymer melt temperatures.…”