碩士 / 國立成功大學 / 航空太空工程學系碩博士班 / 101 / The purpose of this work is to study the thermal stress behavior under a static thermal loading for the annular heat exchangers in order to reduce thermal stress and propose a novel design.Current finite element commercial implicit code - ANSYS WORKBENCH with a size optimization module is used to simulate and optimize the geometry of heat exchanger in the design process.Upon examining numerical thermal expansion results, the maximum stress is occurred on the inner wall of tube beneath bottom surface of fin when the heat exchangers is tolerated with a thermal loading at about 1,200K.Therefore, three designed gaps located on fins are proposed to reduce thermal stress in order to increase the expansion space of fin. In addition, an inner chamfer located on the intersection between gap root and outer tube wall is proposed to further decrease thermal stress in the current simulation. A 41% decrease of thermal stress for the annular heat exchangers with three designed gaps containing inner chamfers is reported when compared with that of original annular heat exchangers.
Thermal conductivity is a significant factor to affect temperature gradient and cooling performance for the annular heat exchanger with specific fins in the current simulation. Therefore, annular heat exchangers with various metallic and ceramic materials (chromium copper alloys, molybdenum alloys, silicon carbide and tungsten carbide) containing different thermal conductivities are presented. Based on present simulated results, the chromium copper alloys annular heat exchanger with fins is first priority because the minimum corresponding thermal stress is reported under thermal loading. When the temperature exceeds its tolerance range, molybdenum alloys is proposed.
| Identifer | oai:union.ndltd.org:TW/101NCKU5295021 |
| Date | January 2013 |
| Creators | Jia-LongDo, 杜佳龍 |
| Contributors | Syh-Tsang Jenq, 鄭泗滄 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 63 |
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