具薄件LED散熱結構之模流分析

Mold Flow Simulation of Thin-Walled LED Heat Sinks

盧奕同(Yi-Tung Lu)

指導教授 ： 周榮源

國立虎尾科技大學/工程學院/機械設計工程研究所/碩士(2013年)

摘要

本文目的是針對真空壓鑄及真空截止閥設計以FLOW-3D分析軟體進行兩大方向探討。第一方向本文以數值模擬方法針對薄件之LED散熱結構以不同熱傳導係數、真空度、模具溫度、進料速度等成型條件進行探討。第二方向探討數值模型真空閥及薄件之LED散熱結構，數值模型所考慮的參數為：LED散熱片之T_1、真空閥之T_2、D_1、D_2、L_1、L_2、W等不同部位尺寸，兩大方向工作流體皆設定為Al 384.0。第一類問題在相同之LED散熱模型、真空截止閥模型、成型條件不同所得到之氣孔缺陷大小不同，真空度過高，材料的緊實度也大，鑄件易出現裂痕，真空度過低降低了排氣效率，鑄件易形成氣孔缺陷。第二類問題在相同熱傳導係數、真空度、模具溫度、進料速度下，T_2可有效觸發機構運作，但過薄或過厚易影響抽真空時間。真空度760Torr、200Torr、100Torr及10Torr之氣含量下降量分別為0.311％、0.174％、0.008％，真空度100Torr降至10Torr之氣含量雖呈現下降，但下降量只有0.008%。

關鍵字

真空壓鑄 ； 真空閥 ； LED散熱結構 ； 數值方法

並列摘要

In this paper, the filling analyses of vacuum die-casting of a thin-walled LED heat sink structure and the vacuum valve structure are simulated by FLOW-3D software. Two topics are analyzed and discussed in this study. First, numerical simulations for variety of molding conditions, including different parameters of thermal conductivity, vacuum pumping pressure, mold temperature, filling velocity, respectively, are conducted for the computational model of a thin-walled LED heat sink with a vacuum shut-off valve. Second, effects of several geometrical parameters, including thickness of LED heat sink, vacuum valve dimensions of T2, D1, D2, L1, L2, W, respectively, of the computational model of a thin-walled LED heat sink with a vacuum shut-off valve are explored. In these two topics, melts are set to liquid metal of Al 384.0 materials. The first topic of analysis mainly to investigate the effects of molding parameters based upon the same computational model of a thin-walled LED heat sink with a vacuum valve. The simulated results show if molding conditions are changed, different sizes of defects are appeared in castings; if vacuum pumping pressure is higher, the casting is also firmness, density prone to increase; if vacuum pumping pressure is too low, then pumping efficiency of mold cavity is low and it will be easy to form the casting porosity defects. For the second topic of analysis, molding conditions are hold constantly, and effects of different geometrical dimensions to quality of castings are simulated. T2 trigger mechanism can effectively operate, but too thin or too thick, it will affect the pumping time to different degrees of vacuum. Decreasing of gas residuals of castings for the vacuum pumping pressures of 760Torr, 200Torr, 100Torr to 10Torr, were 0.311%, 0.174%, 0.008%, respectively. However, the value is only 0.008% for the case of 100Torr to 10Torr.

並列關鍵字

Vavuum die casting ； Vacuum shut-off valve ； LED heat sink ； Numerical simulation

參考文獻

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