为考察装配板状肋片散热器的多角度照射型LED灯的自然对流散热性能的方向效应, 以一款LED投光灯的关键散热结构为研究对象, 采用实验测量法验证数值模拟的计算精度, 并将数值模拟的温度和流体数据用于分析3种驱动电流和7个出光倾角下最大温升和温度均匀性的散热机制。结果表明: 不同倾角下的散热器肋间风道内的流速分布的较大差异, 是导致最大温升和温度均匀性变化的根本原因; 最高温度点的上、下游流速的差值可用于定量解释温度均匀性的变化规律。不同倾角下肋片间距对最大温升的影响趋势表明: 最佳间距附近的散热器性能对倾角的敏感度最高, 散热能力的方向效应不容忽视。

The plate-fin heat sink is widely used in LED lamp for application of multi-angle illumination. According to the key structures of a LED projection lamp, the orientation effects on heat dissipation performance of plate-fin heat sink with natural convection cooling were researched under 3 driving currents and 7 inclination angles between illumination direction and gravity direction. Based on the validity and accuracy of numerical simulation verified by experimental results, the thermal mechanisms with respect to maximum excess temperature and temperature uniformity were investigated through analyzing temperature and flow data derived from numerical simulation. The obvious differences of air velocity distribution in the flow channel of fins are found among inclination angles, these differences are the main reason of sensitive orientation effect about maximum excess temperature and temperature uniformity. In addition, air velocity difference between upstream and downstream around the measuring point with maximum temperature can be used to quantitatively interpret the variation trend of temperature uniformity in different inclination angles. Furthermore, the effects of inclination angle and fin spacing on the maximum excess temperature were analyzed. The results show that the heat dissipation performance of plate-fin heat sink with optimal fin spacing has high orientation sensitivity, so the study of orientation effects on the air flow and heat transfer of plate-fin heat sinks is an indispensable task in the thermal design of LED with multi-angle illumination function.