Application of buckling behavior to evaluate and control shape variation in high-temperature microlamination
| Autor: | Wattanutchariya, Wassanai |
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| Rok vydání: | 2002 |
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| Druh dokumentu: | Thesis/Dissertation |
| Popis: | The miniaturization of energy, chemical and biological systems for distributed and portable applications, known as process intensification, is realized by the enhancement in heat and mass transfer performance within high surface-to-volume ratio microchannels. Fabrication of devices for process intensification is achieved in part by microlamination techniques. These techniques consist of patterning, aligning, and bonding thin layers of material into monolithic devices. Even though the fabrication techniques used in microlamination are generally accurate and consistent, small amounts of dimensional variation in microlaminated structures can strongly affect the device performance. One significant finding of this dissertation is that fin warpage, which is commonly induced during bonding, generally has more adverse device performance effects than misalignment. A heat exchanger that contains fin warpage as small as 25 percent of the microchannel height (on the order of 10 ��m) needs to almost double the number of flow channels to gain the same thermal effectiveness as the uniform one. Therefore, the focus of this dissertation is to investigate, understand, and learn how to control the cause and effect of buckling warpage produced within microlaminated structures. The microlamination discussed in this dissertation is performed with a thermally-controlled registration process, which facilitates metallic bonding at elevated temperatures. Another finding of this dissertation is that the tolerance limits of the fixture used in this registration process exceed the accuracy of the machine tools used to produce the fixture. Fixture tolerance limits on the order of 10 ��m are necessary to align and bond laminae with thicknesses below 100 ��m. An alternative technique based on the compliance of the fixture is proposed in order to improve these limits. This technique helps compensate for the excessive registration force due to over-constrained bonding, which extends the range of fixture tolerance limit to over 100 ��m well within current process capability of machine tools. Another approach to controlling fin warpage, based on the induction of higher modes of fin buckling, is also discussed. An analytical evaluation shows that the effect of fin warpage is minor as the mode of buckling reaches mode 10. A preliminary experiment confirms that the induction of fin buckling into a higher mode can be achieved by constraining the fin at specific locations along the fin during microlamination. Graduation date: 2002 |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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