本研究解決無人機鋰離子電池模組散熱之問題，散熱模組使用針狀鰭片熱沉搭配均溫性優異的鋁均溫板以達到良好散熱效果。首先採用文獻之理論方法分析無側邊旁通的狀況，電池模組使用MATLAB曲線擬合估算21700單電池在6C下的發熱率為5.04W。在無人機飛行速度10m/s下，熱沉使用Khan經驗公式求得交錯排列之針狀鰭片在最佳無因次橫向間距l_T=1.5~1.75時有最大熱傳率。當考慮無人機的無定向飛行時，採用圓形熱沉底板，在有側邊旁通流的狀況，使用ANSYS Fluent對無側邊擋板的半圓形熱沉進行數值模擬。經與正方形排列的針狀鰭片比較後，採用性能較佳的正三角形排列針狀鰭片熱沉。真實使用之熱沉體積龐大，因此模擬不同底板直徑下之鰭片最佳間距，透過外插之方式得到底板直徑600mm的鰭片無因次最佳間距(l_T)為3.6，並且在操作溫度45℃之限制下，計算得針狀鰭片之長度為850mm可解決電池模組產生之熱量，此長度之鰭片效率低落且重量也會帶來負面影響，故將鰭片長度改至100mm，雖此鰭片長度會讓底板溫度T_base升至55.5℃，但電池模組本身也將受到強制對流之影響，有機會讓T_base接近45℃。另外，選定一種尺寸之熱沉探討具側邊旁通流下不同入口角度與局部對流熱傳係數。考慮0°, 15°, 與30°三種氣流方向的加權平均結果顯示，在底板直徑120mm中，當D=3mm且鰭片高度大於25mm時可達到電池溫度小於45℃的限制。

This study investigates the heat dissipation of the UAV (unmanned aerial vehicle) lithium-ion battery module, using an aluminum vapor chamber with pin fin heat sink to achieve temperature uniformity and sufficient heat dissipation capacity. For conditions without side bypass, the 21700 battery module uses MATLAB curve fitting to calculate the heating rate at 6C is 5.04W. At a UAV flying speed of 10m/s, the maximum heat dissipation rate for the pin fin heat sink with staggered arrangement exists at dimensionless transverse spacing l_T=1.5~1.75, calculating using the Khan empirical formula. As a UAV flies in an arbitrary direction, a circular pin-fin heat sink with side bypass airflow is analyzed numerically using the commercial ANSYS Fluent software. The pin fins are arranged in an equilateral triangle pattern, which is preferred to a square pattern according to numerical comparison. The actual use of heat sink is too large for direct simulation. So, different base plate diameters are simulated to get respective optimal spacing, and the dimensionless optimal spacing of D_b=600mm heat sink is estimated by extrapolation to be 3.6. Under the limit of temperature of 45℃, estimated the length 850mm of pin fin can solve the heat generation by battery module. The efficiency of this length is low and the weight will also have a negative impact. Therefore, the length of the fins is changed to 100mm. Although this fin length will increase T_base to 55.5℃, the battery module will also be cooled by forced convection, which may make T_base close to 45℃. In addition, a size of heat sink is selected to discuss different inlet angles and local convective heat transfer coefficients with side bypass flow. Considering the weighting average of three directions of 0°, 15°, and 30° to represent the arbitrary flying direction, the 45℃ limit for the lithium-ion battery temperature can be met with D=3mm and a fin height > 25mm.

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