本文以CFD軟體結合傳統逆向方法來分析管式熱交換器於自然對流之熱傳及流動特性，並配合實驗數據來驗證其準確度，透過創新型U型加熱管及傳統板式熱交換器來深入研究管間距及角度之變化所造成之影響，期望能得到最佳效率之組合。結果顯示流動模式選用Zero-equation最省時且不失精準，透過分析實驗及模擬數據可以發現，當U型管軸向平行於熱板時，散熱效率隨管間距的提升而增加；而U型管軸向垂直於熱板時，則是較小之管間距，散熱效率較佳，因此在探討熱源間距時，應同時考慮U型管之擺放方式，不同U型管擺放方向對於空腔之對流發展影響甚大，且U型管傾斜角度之變化，對於模型之熱傳性能也會有所不同，當中又以45˚傾斜時熱傳效率最好，最後發現該模型於Lv = 100 mm、θ = 45˚及 α = 0˚之組合時，整體對流發展較完整，熱傳性質也最佳，與最低效率之模型相比有著42% 之差距。

This study combines Computational Fluid Dynamics (CFD) simulation with traditional inverse method to analyze the heat transfer and flow characteristics of tube heat exchangers under natural convection. The experimental data is used to verify the accuracy of simulation. By using innovative U-shaped tube heater and plate heat exchanger, this study aims to investigate the effects of variation in tube spacing and angles. The goal is to identify the optimal combination for the highest efficiency.
The numerical results with experimental data show the Zero-equation model is the most preferable flow model in this paper. Additionally, when the placement angle of U-tube (α) is 0˚, the heat dissipation efficiency increases with larger spacing. On the other hand, when the placement angle of U-tube (α) is 90˚, smaller spacing shows better heat efficiency. Therefore, it is significant to consider both spacing and placement direction simultaneously as investigating the placement angle of U-tube. Changes in the inclination of U-tube also result in variations in the heat performance of the model. Among these variations, the asymmetric structure with θ = 45˚ demonstrates the best performance.
Finally, it was found that the model with the combination of Lv = 100 mm, θ = 45˚, and α = 0˚ has the most complete development of convective flow and the optimal heat transfer efficiency. Compared to the lowest ones, there is a difference of 42% in heat transfer efficiency.

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