本文針對環狀熱交換器在受熱負載後，產生熱應力之情形，並且設計出新的鰭片外型來減少所產生之熱應力，設計的過程以有限元素軟體ANSYS WORKBENCH 來做應力分析，並利用其最佳化模組得到最後的幾何尺寸，在熱交換器之內部環境溫度為1200K下，鰭片因熱膨脹造成擠壓，使最大應力出現在管件內壁，因此設計出三個空隙，使得鰭片有了膨脹空間，此外，空隙的根部與管件外壁交接處為內倒角形狀，目的皆是為了減少熱應力大小，而新的設計減少了41%應力值。
另外，探討不同的金屬及陶瓷材料與熱應力之關係，材料分別為鉻銅合金、鉬合金、碳化矽以及碳化鎢四種,熱傳導係數將影響溫度梯度與散熱效果，熱交換器的材料若具有較佳的熱傳性，則受熱負載下所產生的熱應力較小，並且散熱能力較好，因此在選用熱交換器的材料時，熱傳導係數是很重要的因數，在四種熱交換器材料當中，鉻銅合金之散熱效果較好，所產生的熱應力也較小，是最優異的選擇，但鉻銅合金在四者中熔點最低，若溫度超過其容忍範圍，則推薦鉬合金。

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.

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