摘要
以100 W向下照射的LED灯为研究对象,计算了在单纯导热、热辐射和导热耦合以及对流、热辐射和导热耦合3种情况下透镜的温度及热应力分布,并对透镜外表面特征点的温度变化进行了测量。研究了透镜封闭腔内空气热对流和表面热辐射对透镜温度分布的影响,分析了表面发射率对透镜中心温度的影响以及热膨胀系数对最大热应力的影响。实验结果表明:热对流对透镜温升的影响不足1%,热辐射对透镜中心温升的影响为13.3%。透镜中心温度随光源及透镜表面发射率近似呈线性变化,最大热应力也随热膨胀系数呈线性变化。最大热应力集中在透镜的边角处,而最大变形总位移却位于透镜中心。因此,在大功率LED透镜设计过程中,在满足光学要求的前提下,可考虑涂覆低发射率的涂层来降低透镜温度。同时,为减小热应力及热变形,应尽量避免边角结构,选择热膨胀系数较小的材料。
A downward-illuminated 100 W LED was studied herein, and its temperature and thermal stress distributions were calculated under three conditions: pure thermal conduction, thermal radiation and thermal conduction coupling, and convection, thermal radiation, and thermal conduction coupling. The following factors were evaluated: temperatures of the characteristic points on the lens’ external surface;the effects of air convection in the closed cavity of lens and surface radiation on the lens’ temperature distribution;the effect of surface emissivity on the central temperature of the lens;the effect of the thermal expansion coefficient on the maximum thermal stress. Results show that thermal convection produces a negligible rise in temperature(less than 1%), whereas surface radiation results in a 13.3% temperature rise at the lens’ center. The temperature of the lens’ center varies approximately linearly with the light source’s emissivity and the lens surface area, whereas the maximum thermal stress varies linearly with the thermal expansion coefficient. The maximum thermal stress is concentrated at the lens’ corners, whereas the maximum total deformation displacement is concentrated at its center. Therefore, when designing high-power LED lenses, a low-emissivity coating should be considered to reduce the lens’ temperature while still satisfying the optical requirements. To reduce thermal stress and deformation, a material with a small thermal expansion coefficient should be used and the lens’ corners should be avoided.
作者
许丹丹
胡学功
Xu Dandan;Hu Xuegong(Research Center for Heat and Mass Transfer,Institute of Engineering Thermophysics,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2019年第10期267-273,共7页
Acta Optica Sinica
基金
国家重点研发计划(2017YFB0403200)
关键词
光学器件
LED透镜
热辐射
温度分布
热应力
optical devices
LED lens
thermal radiation
temperature distribution
thermal stress
