Investigation of the use of Alphaflex/high density polyethylene composites as suitable materials for large diameter deep ocean cold water pipes
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2006
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Abstract
Alphaflex, an impact modifier for elastomers and thermoplastics, has been compounded with High Density Polyethylene (HDPE). The physical properties of the modified plastic were tested to see if the new material is physically and economically viable to be used as the cold water pipe material in OTEC applications. The main area of research conducted on the cold water pipe material was determining the effect of enhancement of HDPE with Alphaflex on hoop strength of the pipe. The effects realized were then analyzed for physical and economic viability for various ocean thermal energy conversion and seawater district cooling scenarios. All physical properties of the Alphaflex enhanced material tested exhibited favorable results when compared to HDPE. The comparison of the two materials is as follows.
Key Characteristics Process Parameters Results
Physical Property Test Method Unit Alpha1 Alpha2 Alpha3 HDPE
Flexural Strength D790 psi 3800 3500 3600 1400
Tensile Strength, Yield D638 psi 5090 5090 5010 3200
Izod (notched) D256 ft Ibf/in 9.20 10.7 8.50 4.0
Specific Gravity D792 Dimensionless 0.96 0.96 1.01 0.954
Results from the analysis of the test results indicate that for floating OTEC plants with 3,280 ft long 6.5 ft diameter pipes, power output and revenues can be increased by as much as 70%. This greatly offsets the additional cost of the more expensive enhanced plastic cold water pipe material. Scenarios that require long pipes or supply small loads without room for expansion do not offer as great an advantage and in some cases are not able to meet economic expectations under the current production costs of Alphaflex. The cost to produce Alphaflex would be greatly reduced if it were used in the manufacturing of cold water pipes, as the volume produced would grow quite significantly and production cost is linked directly to volume.
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Thesis (M.S.)--University of Hawaii at Manoa, 2006.
Includes bibliographical references.
vii, 49 leaves, bound ill. 29 cm
Includes bibliographical references.
vii, 49 leaves, bound ill. 29 cm
Keywords
Water-pipes -- Design and construction, Pipe, Plastic -- Design and construction
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Ocean and Resources Engineering; no. 4093
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