熱電材料應用於地熱系統之分析與模擬

Study of Thermoelectric Material Applied to Geothermal System

楊柏俊(Bo-Jiun Yang)

指導教授 ： 馬小康

國立臺灣大學/工學院/機械工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601885

摘要

近年來能源短缺的問題日益嚴重，因此廢熱回收成為一個十分重要的議題。而熱電材料在此扮演了一個重要的角色。在地熱廠的管路上，由於會有熱量的散失，因此可以利用熱電材料將其廢熱加以回收，利用管路的熱量散失提供穩定的熱源。
本研究主要專注於模擬熱電材料在地熱模組下的廢熱回收情形，而在本論文中以實驗與模擬分別論述。在實驗方面，首先探討單片熱電材料的廢熱回收情形，其次在探討熱電材料在地熱模組中的廢熱回收情形。而在模擬方面，首先以AnsysWorkbench 中的Thermoelectric 模組模擬熱電材料的廢熱回收情形，其次在以AnsysWorkbench 中的Fluent 模組模擬熱電材料在地熱模組中的共軛熱傳，並且再搭配Thermoelectric 模組模擬熱電材料在地熱模組中廢熱回收的情形，最後再以實驗與模擬相互比對來作探討。
實驗結果發現，工研院所提供的熱電材料TEG616-6 為非常高效能的低溫型熱電片，其開路電壓，輸出功率以及內電阻會隨高溫端升高而升高，當其高溫端為200℃，低溫端為30℃時，其輸出功率可以高達5.42W，其功率密度為3387.5푊⁄푚2，效率約為5%。而在地熱模組方面，當熱水端為90℃，冷水端為25℃時，其輸出功率可以到達2.6529W，而功率密度為414.515푊⁄푚2。在單片熱電片模擬方面，以熱電參數的驗證結果而言，電阻率以一次回歸曲線加上介金屬層修正最為適合，席貝克係數以二次回歸曲線預測最為適合，熱導率也以二次回歸曲線預測最為適合，其熱電片廢熱回收效益與實驗誤差甚小。在地熱模組模擬部分，以紊流模型與穩態能量方程式模擬，其與實驗誤差相距甚小。由於本論文中的熱電材料可以分析至 200℃高溫，因此在本論文的最後有作出當地熱水超過100℃時之廢熱回收情況，模擬結果顯示當熱水端方面則是100℃、125℃、150℃、175℃以及200℃其最大輸出功率可以達到3.68W、5.55W、8.68W、13.92W 以及18.66W。

關鍵字

地熱 ； 熱電材料 ； 廢熱回收 ； 熱電模擬 ； 共軛熱傳

並列摘要

In recent years, the problem of shortage of energy is growing up, therefore, waste heat recovery have become a very important issue. And the thermoelectric material plays an important role in this issue. A geothermal plant, since the heat is lost in the pipeline, we can use the thermoelectric material to recover the waste heat, and utilize dissipated heat as a stable heat source.
The aim of this study is to simulate the situation of the waste heat recovery with the geothermal module. In this thesis, the experiment and simulation are discussed. In the experiment, we investigate the case of waste heat recovery with single thermoelectric generator, followed by the geothermal module. In the simulation, we simulated the single thermoelectric generator by the Thermoelectric module in the Ansys Workbench, followed by the geothermal module which was simulated by the Fluent and the Thermoelectric module in the Ansys Workbench. Finally, we compared and discussed the experimental and simulated data.
The result shows that the thermoelectric generator TEG616-6 provided by ITRI is a high-performance thermoelectric generator,. The open circuit voltage, output power, and the internal resistance of the thermoelectric generator all increase with the elevating temperature of the high-temperature side,. When the high-temperature side was at 200℃,and the low temperature side was at 30℃, the output power can reach 5.42W, the power density was 3387.5W⁄m^2 , and the efficiency was about 5%. In terms of geothermal module, when the hot water side was at 90 ℃, and the cold water side was at 25℃, the output power can reach 2.6529W, and the power density was 414.515W⁄m^2 ,. In the simulation of the single thermoelectric generator, according to the verification process,the electrical resistivity can be predict by the first order regression analysis with intermetallic layer modification,. The seebeck coefficient and thermal conductivity can be predict by the secondary order regression analysis. In the simulation of the geothermal module, we utilized the turbulence model and the steady energy model to approach the practical situation. After comparing the experimental data with the simulated data, it shows the error is very small. In the end of the thesis, we can predict the performance of the geothermal module with the hot water temperature exceeding 100℃,. The simulation result shows that when the hot water side was at 100℃, 125℃, 150℃, 175℃ and 200℃as well as the cold water side was at 25℃, the maximum output power can reach 3.68W,5.55W, 8.68W, 13.92W and 18.66W.

並列關鍵字

Geothermal energy ； Thermoelectric material ； Waste heat recovery ； Thermoelectric simulation ； conjugate heat transfer

參考文獻

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