Simulation of sag during the solidification of extruded plastic pipe /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1992.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | When plastic pipe is extruded, it emerges from an annular die and passes through a sizing sleeve to set its outer diameter. The pipe is then solidified in a cooling tank by spraying the outer surface with cold water. For thick walled pipe, material on the inside stays molten for a long time, and flows under its own weight. This gravitational flow (or sag) can cause serious non-uniformity in the wall thickness profile. The objective of this dissertation is to simulate this combined fluid flow and heat transfer with phase change problem. The coupled partial differential equations that govern sag flow were solved numerically using a high order finite element technique called the spectral element method. The results of the computer simulations showed the solid pipe wall thickness predictions to be comparable with data taken from an actual plant trial, with the maximum deviation being only 7%. The simulations were also able to accurately predict the location within the cooling chamber where the pipe became completely frozen. Parametric studies were carried out to determine the effects of process parameters such as initial eccentricity, average extrusion temperature and cooling water temperature on pipe thickness distribution. One useful result was the determination of the optimum mandrel position for solidification of extruded pipe. Since the simulations were carried out in dimensionless form, the model can be used to calculate the optimum mandrel position and the corresponding minimum waste fraction for each size and series of pipe on a given extrusion line. Finally, a new way was proposed to make pipe that would eliminate sag altogether. The proposed technique is to rotate the pipe while it is solidifying in the cooling chamber. The spectral element simulations predicted that a uniform pipe could be produced by rotating pipe within the range of 0.1 to 1 rev/min. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Interdisciplinary Engineering." |
| Physical Description: | xv, 282 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |