高碳醇/膨胀石墨复合相变热沉多目标优化

为解决高温工作环境下电子芯片的发热问题，设计采用相变材料（PCM）的控温模块，建立相变材料的控温模块模型。相变材料选择高碳醇/膨胀石墨复合材料。借助FLUENT软件进行数值模拟，探究在相同加热功率下，加热面积对控温时间的影响。对控温模块的几何尺寸进行参数分析，将数值模拟结果用于训练人工神经网络，实现对控温时间的预测。根据芯片发热功耗、芯片尺寸，通过NGSA-Ⅱ多目标优化算法优化控温模块几何尺寸，延长控温时间，降低模块质量。最终得到一系列非支配解集，可根据控温时间需求选择合适的模块尺寸设计。针对长宽为35.4 mm、发热功率为15 W的芯片进行控温模块优化设计。环境温度为80℃，温控目标小于90℃，控温时间180 s，优化后模块减重13.0%，模块内温度与液相分布也更均匀。 

Multi-objective optimization of a high alcohol/expanded graphite composite PCM based heat sink

A novel composite Phase Change Material (PCM) based heat sink is proposed to cool chips under high ambient temperature. Physical and numerical model is proposed for the heat sink. High alcohol/expanded graphite composite material is chosen as PCM in the heat sink. Numerical model is obtained with the help of FLUENT software for three-dimensional simulation. The effect of heated area on the chip's operation time under same thermal output is investigated. Parameter analysis is performed on the geometric dimensions of the heat sink. Artificial neural network is trained with numerical results to predict the operation time of a given heat sink/chip configuration. NGSA-Ⅱ multi-objective optimization algorithm is employed to optimize the geometric shape of heat sink based on chip size and power output. The main objective is to stretch operation time while reducing the total weight of the heat sink. A series of non-dominate solution is obtained so that optimal geometric design can be chosen based on operation time needs. The optimization process is carried out to obtain the optimal heat sink design to cool a chip, whose side length is 35.4 mm with constant power output of 15 W. The ambient temperature is 80℃ while the chip needs to be kept under 90℃ for a sustained operation time of at least 180 s. After optimization, the weight of heat sink is reduced by 13.0%. The temperature and the liquid fraction distribution are more uniform.