Extrusion of non-Newtonian fluids in a single-screw extruder with pressure back flow.: An article from: Polymer Engineering and Science
Book Details
PublisherSociety of Plastics Engineers, Inc.
ISBN / ASINB00093UD14
ISBN-13978B00093UD19
MarketplaceFrance 🇫🇷
Description
This digital document is an article from Polymer Engineering and Science, published by Society of Plastics Engineers, Inc. on February 15, 1996. The length of the article is 5755 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.
From the author: The transport phenomena underlying the extrusion of non-Newtonian fluids in single-screw extruders is investigated numerically and experimentally. The viscosity of the investigated fluids is a strong function of the temperature and, for the non-Newtonian case, of the shear rate. Therefore, the governing equations of motion are coupled to the energy equation through the viscosity. The velocity in the down channel direction of the screw extruder is a result of both shear and pressure driven transport. The pressure acts in a direction opposite to that of the drag flow, and comparatively high pressures arise at the die in typical extruders. When a narrow die is used in the screw extruder, the pressure gradient in the down-channel direction becomes so large that the down-channel velocity near the screw root becomes negative in terms of the coordinate system fixed to the screw. The conventional marching schemes fail to simulate the fluid flow when the down-channel velocity becomes negative, since the downstream conditions are not known. Two different numerical schemes used to simulate the fluid flow in a single-screw extruder for this circumstance, which often arises when dies with high flow resistance are used and which is termed as pressure back flow in the literature, have been discussed. One scheme is based on including the down-channel thermal diffusion, making the problem elliptic, and the other scheme uses a different coordinate system. Both formulations are found to yield results that are fairly close. Experiments were also carried out to measure the pressures at three different locations in a single-screw extruder. The computed results were found to be in good agreement with the experimental results. The pressures at the die obtained numerically by treating the flow as isothermal are found to be lower than those obtained when the flow is treated as nonisothermal, indicating the strong influence of thermal transport in this problem.
Citation Details
Title: Extrusion of non-Newtonian fluids in a single-screw extruder with pressure back flow.
Author: Raman V. Chiruvella
Publication:Polymer Engineering and Science (Refereed)
Date: February 15, 1996
Publisher: Society of Plastics Engineers, Inc.
Volume: v36 Issue: n3 Page: p358(10)
Distributed by Thomson Gale
From the author: The transport phenomena underlying the extrusion of non-Newtonian fluids in single-screw extruders is investigated numerically and experimentally. The viscosity of the investigated fluids is a strong function of the temperature and, for the non-Newtonian case, of the shear rate. Therefore, the governing equations of motion are coupled to the energy equation through the viscosity. The velocity in the down channel direction of the screw extruder is a result of both shear and pressure driven transport. The pressure acts in a direction opposite to that of the drag flow, and comparatively high pressures arise at the die in typical extruders. When a narrow die is used in the screw extruder, the pressure gradient in the down-channel direction becomes so large that the down-channel velocity near the screw root becomes negative in terms of the coordinate system fixed to the screw. The conventional marching schemes fail to simulate the fluid flow when the down-channel velocity becomes negative, since the downstream conditions are not known. Two different numerical schemes used to simulate the fluid flow in a single-screw extruder for this circumstance, which often arises when dies with high flow resistance are used and which is termed as pressure back flow in the literature, have been discussed. One scheme is based on including the down-channel thermal diffusion, making the problem elliptic, and the other scheme uses a different coordinate system. Both formulations are found to yield results that are fairly close. Experiments were also carried out to measure the pressures at three different locations in a single-screw extruder. The computed results were found to be in good agreement with the experimental results. The pressures at the die obtained numerically by treating the flow as isothermal are found to be lower than those obtained when the flow is treated as nonisothermal, indicating the strong influence of thermal transport in this problem.
Citation Details
Title: Extrusion of non-Newtonian fluids in a single-screw extruder with pressure back flow.
Author: Raman V. Chiruvella
Publication:Polymer Engineering and Science (Refereed)
Date: February 15, 1996
Publisher: Society of Plastics Engineers, Inc.
Volume: v36 Issue: n3 Page: p358(10)
Distributed by Thomson Gale
