本文旨在建立一種簡單快速的三維熱阻模型，可以對熱電能源廢熱回收系統的發電效能進行估算。熱電能源廢熱回收系統包含了三個部分：廢熱回收腔、熱電能源產生器、冷卻系統。系統發電量的估算對於優化系統有很大的幫助。數值流體力學一向在優化系統上有很好的表現，俱備正確且全面的熱流場分析。可惜的是，越精確的預測基本上就需要越多的時間進行數值計算。熱阻模型分析中，不對方程式進行離散，而是應用熱阻關係以及能量守恆的概念，對於系統的溫度分佈進行計算。在本文中，對一個熱電能源廢熱回收系統建立熱阻模型，同時，同一個熱電能源廢熱回收系統也在數值模擬軟體FloTHERM中進行數值計算。最後，將此系統進行實驗量測，再與熱阻模型分析出的結果作比較。與FloTHERM的模擬結果比較中，兩者在熱電能源產生器冷熱兩端的溫度差異約在5 %；而與實驗結果進行比較時，差異約為10%。這樣的一致性表示出此三維熱阻模型能夠描述出系統的機制。在改變不同的參數時，可以很快地建立出來不同的參數與系統發電量之間的關係。從熱阻模型計算出的結果，能夠發現熱電能源產生器放置在廢熱回收腔的位置與腔體內的流場分佈對系統發電量有很大的影響；同樣的擺放方式，在不同的流場分佈下，可能會出現兩極的結果。另外，系統發電量對於內外流場流速的改變有不同的敏感度，透過三維熱阻模型快速的計算，可得到不同情況下增加系統發電量最有效率的方法。因此，本文所發展出的三維熱阻模型對於系統的優化有很大的助益。

This thesis is aimed to the optimization of a waste heat recovery system with thermoelectric generators (TEGs). The system will be optimized by developing an efficient three-dimensional (3D) thermal resistance model. In this thesis, it is shown that analysis of three-dimensional (3D) thermal resistance model is a rapid and simple method to estimate the power generated from a waste heat recovery system with thermoelectric generators (TEGs) and assists to optimize the system. The estimation of generated power is an important part of the system design. Methods of Computational Fluid Dynamics (CFD) assist the analysis and improve the performance with great accuracy but great computational duration. The use of this method saves much time relative to such CFD methods. In 3D thermal resistance model, a node of unknown temperature is located at the centroid of each cell into which the system is divided. The relations of unknown temperatures at the cells are based on the energy conservation and the definition of thermal resistance. The temperatures of inlet waste hot gas and ambient fluid are known. With these boundary conditions, the unknown temperatures in the system are solved, enabling estimation of the power generated with TEGs. A 3D model of the system was simulated with FloTHERM; its numerical solution matched the solution of the 3D thermal resistance model less than 5 %. The power generated with the same system with TEGs (TMH400302055, Wise Life Technology, Taiwan) was measured; the experimental result is consistent with the result obtained from the 3D thermal resistance analysis; the relative deviation is approximately 10 %. The power generated is affected by many variables; the positions of the TEGs, the uniformity of the internal flow of the velocity profile and the internal and external flow velocities are considered in our 3D thermal resistance model analysis. According to the results, both the positions of the TEGs and the uniformity of the internal flow of the velocity profile should be taken into account to maximize the power generation. Under varied operational conditions, the power generated from the system might be more sensitive to the velocity of either the internal or external flow. Choosing an appropriate method makes increasing the power generation efficient. The relations between variables and power generation are readily revealed, even with varied parameters, yielding an optimal design of a waste heat recovery system.

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