熱電致冷元件的效能除了與熱電材料性質相關之外，亦受其操作條件及熱電材料幾何形狀所影響。本研究中定義一簡單的操作因子IG（操作電流乘以熱電材料的幾何形狀），並探討此操作因子對熱電熱電致冷元件性能之影響。研究發現經由簡單數學推導可求得達到最大熱電效能的幾何操作因子。接著以理論分析結果為基礎來討論熱電致冷元件中的電流密度分佈對其熱電效能的影響。此部分利用ANSYS有限元素分析軟體建立二維及三維的熱電模型，並藉由改變熱電材料長度來討論元件中電流不均勻性對熱電效能的影響。由模擬結果發現熱電材料長度變短後會使得電流壅塞效應越來越嚴重，而造成冷端與熱端的溫度差變大。因此從熱端回流到冷端的熱太多而造成效能下降。另外針對縮小接觸面積並施加均勻電壓與均勻電流兩種不同的負載，討論不同的電流分佈對熱電效能的影響。從模擬結果發現考慮接觸電阻效應之後會使得溫度差下降，且當負載為均勻電流時會使得接觸電阻所產生的焦爾熱大幅上升，進而使得冷端溫度上升，降低熱電致冷元件性能。

Abstract

The efficiency of thermoelectric cooler is not only affected by the properties of thermoelectric materials but also by the operating conditions and geometry of thermoelectric materials. In this research, we investigated the performance of the thermoelectric cooler by defining a geometric operation factor, IG, which is the applied current multiplied by the geometry of thermoelectric elements. We can calculate the optimized geometric operation factor to achieve the best performance of thermoelectric coolers. The effect of electric current distribution on the performance of thermoelectric devices is also discussed based on the theoretical analysis results. In this part, we build the 2D and 3D thermoelectric models using ANSYSTM FEA software, and explore the influence of non-uniform current in the thermoelectric elements. The simulation results indicate that the degree of current crowding in thermoelectric elements increases with decreasing length of TE elements. The longer TE elements result in larger temperature difference between both ends of TE elements. Therefore, there will be a marked conductive heat flowing from the hot side to the cold side, which degrades the performance of thermoelectric devices. According to the simulation results, it is found that the contact resistance effect causes the reduction of temperature difference. When the device loading is uniform current, the contact induced joule heat will raise the temperature at the cold side and decrease the performance of thermoelectric devices.

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