本論文利用商業套裝軟體CFD-ACE+建立具肋材之管式熱交換器之三維模型，並透過拉凡格氏法(Levenberg-Marquardt Method)最佳化散熱鰭片之外形參數，以提升熱交換器之熱性能指標為目的來反算出含肋材之散熱鰭片之最佳化形狀。
本研究以文獻[1]為設計基礎並將其延伸，探討四種不同參數設計，並使用反算設計問題預測最佳散熱鰭片外形參數。案例一預測一組肋形散熱鰭片放置位置及高度，並與文獻[1]之結論相比，探討其外形改變對熱性能指標影響之趨勢；案例二將案例一中肋材之位置、高度分開於不同流道中作個別設計，並將其皆列為預測參數；案例三與案例四分別以兩組及三組肋材為初始設計，並將兩組與三組肋材之位置與高度列為參數，探討其各組參數改變對熱性能指標之影響，以上案例設計目標皆為取得熱交換器之最大熱性能指標。
由統計分析的結果顯示，經過最佳化設計後之熱交換器與無放置肋材之熱交換器相比，其平均紐賽數增加了36%，最大熱性能指標達到1.1343，達到本文之具肋材之管式熱交換器最佳化設計的目標。

A three-dimensional design problem is carried out in this thesis to examine the thermal-hydraulic characteristic of a heat exchanger with the Z-shape internally lateral fins with ribs. The objective is to utilize the commercial package CFD-ACE+ and the Levenberg-Marquardt Method (LMM) to estimate the optimal shapes of the ribs and to maximum the thermal performance factor of the heat exchanger.
The present work is to extend the research findings in [1] and to estimate the optimal rib shapes of the Z- shape internally lateral fins in four different cases under a fixed fin volume constraint to yield optimal thermal performance factor. In case A, one pair of rib with same rib position and rib height is considered and the design variables are taken as rib position and rib height. In case B, also considers one pair of rib, however, the rib positions and heights for the upper and lower ribs are different, i.e. there are four design variables in the case. In cases C and D, two and three pairs of ribs are considered, respectively, and the design variables are the rib positions and heights, i.e. the design variables are 4 and 6 for cases C and D, respectively.
Results indicated that case C can obtain the best thermal performance factor among all cases, its average Nusselt number and thermal performance factor are found 36% and 13.4% higher than those in the case without ribs. Besides, case D has the worst performance in thermal performance factor, and this implies that more pairs of ribs cannot guaranty better thermal performance factor.

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