基于植物叶片自适应热结构的仿生均热板多尺度设计理论

With the development of photoelectric products towards the direction of being highly integrated and miniaturized, heat dissipation problem becomes increasingly serious, which has become the bottleneck of industrial application. Vapor chamber is a kind of heat transfer components provided with big isothermal area by means of phase change. Theoretically the heat dissipation capacity of vapour chamber could be one hundred times that of the same material, but the actual heat transfer performance is limited by its structural parameters, such as the topology structure of the internal microchannels, the wick position and size, the capillary attraction, the support column, the chamber thickness and so on. Currently, there is no other effective method to optimize the thermal structure of the vapor chamber. Inspired by the adaptive response and the same principle of heat dissipation of plant leaves, the applicant puts forward a new design theory for vapor chamber based on the adaptive thermal strucuture and multi-scale microchannels of foliages. The key parameters of plant leaves beyond its biology characteristics, especially those of the weatherproof plant leaves, are expected to be achieved and used in biomimetic design for vapour chamber through the mechanism investigation into the relationship between the multiscale microchannel structure and highly efficient fluid transportation, transpiration, and heat dissipation. Furthermore, how the excellent topology pattern of leaf's vascular cambium which integrates the function of fluid transportation and mechanical support makes an impact on the thermal and mechanical coupling performance is also expected to be investigated. The thermal constituent relationship between the foliage microchannel and heat dissipation in multiscale are expected to be obtained through experimental and numerical method, and as a result, the biomimetic criteria and the new multiscale design theory for vapour chamber will be achieved . In the same time, the internal structural optimization and heat dissipation efficiency of vapour chamber are hoped to be realized and raised.

随着光电产品日益小型化和高度集成化，光电产品的散热问题日趋突出，成为制约其发展的主要瓶颈之一。均热板是一种用于提供大等温面的相变传热元件，理论上其散热性能可优于同种材料百倍以上，但其实际传热性能受制于包括内部微通道拓扑结构、吸液芯位置与尺寸、毛细吸力、支撑柱、板厚等若干参数，目前尚无较好方法优化均热板的热结构。申请人受植物叶片自适应散热原理启发，提出基于植物叶片自适应多尺度微通道热结构的仿生均热板设计新理论：拟通过探索植物叶片，尤其是耐候性植物叶片多尺度微通道结构与多孔表面高效传液、蒸腾和散热机理，以及集支撑功能与传质功能于一体的植物叶片维管的精巧拓扑结构对叶片的热力耦合影响，寻找生物因素之外的可应用于均热板仿生设计的关键因素。通过实验与数值方法，建立植物叶片多尺度微通道传液散热的热本构关系和仿生准则，获得新型仿生均热板多尺度设计理论，优化其内部结构参数,提高均热板的散热效率。

随着光电产品日益小型化和高度集成化，光电产品的散热问题日趋突出，成为制约其发展的主要瓶颈之一。均热板是一种用于提供大等温面的相变传热元件，理论上其散热性能可优于同种材料百倍以上，但其实际传热性能受制于包括内部微通道拓扑结构、吸液芯位置与尺寸、毛细吸力、支撑柱、板厚等若干参数，目前尚无较好方法优化均热板的热结构。本项目首先通过实验、仿真和理论的方式，分别从多尺度下研究了耐候性植物叶片的传热传质特性。宏观尺度下，通过光源照射，荧光染料染色，获取了植物叶片中液体的流动图像，经图像处理手段获取了不同种类植物叶片中液体流动速度。细观和微观尺度下，分别测量并统计了不同植物叶片各级脉的解剖结构特征和主脉维管束次生壁增厚的结构与尺寸，建立了仿植物叶脉微通道的三维模型，对其传质、传热性能进行了仿真分析。微观尺度下，分析比较了几种常见气孔形状的结构优劣性，选取了性能优越的球体结构进行传热理论计算，分析了其结构在传热方面的优势。然后，提出了一种基于真实植物叶脉系统的由带渗透壁的叶脉分形网络和多孔组织形成的概念结构，通过建立吸液芯的流阻模型和渗透率模型分析了相应的流动性能。研究结果表明，基于叶脉的分形吸液芯结构能够提供较大的毛细压力，同时能够减小流阻，提高渗透率。因此可以被认为是在吸液芯的两个关键参数，即驱动力以及渗透率之间找到了一个平衡点，具有重要的意义。最后，通过化学腐蚀方法对仿生均热板吸液芯进行了试制，并通过实验研究了其相关性能。当使用去离子水和酒精作为工质时，均热板冷凝端上表面最高温与最低温之间的温度差分别为1.6℃和0.7℃，均温性非常好。在输入功率为140 W时，均热板热阻仅为0.0667 ℃/W，远低于目前许多研究中所获得的热阻。而且，吸液芯的渗透率高达2.568E-10 m2，远大于目前许多研究中所获得的渗透率。因此，基于植物叶脉系统的概念吸液芯结构，完全可以应用于均热板的设计当中，且具有优异的散热与传质性能。