飞秒激光诱导表面纳米周期结构对多相流传热的增强效应

The new technology of multi-phase flow heat transfer holds the properties such as high heat flux, high heat transfer efficiency and high temperature control accuracy, and it is applied to high efficiency refrigeration of giant data center, aircraft loading refrigeration where the space is limited, and high energy laser chilling, et al. With the purpose of enhancing the multi-phase flow heat transfer efficiency and modulating the phase change states artificially, recently researchers are fabricating micro-structures with the sizes from 10 microns to 100 microns on the surfaces which are contacted with the phase change materials. For the sake of investigate the purpose more deeply, we plan to manufacture periodic nano-structures by employing femtosecond laser with various parameters, and study the heat transfer enhancement of the nano-structures with phase change materials. The project is the pioneer investigation internationally to combine the advance fabrication method of femtosecond laser micro- or nano-fabrication with the field of heat transfer or refrigeration. Specifically, the project contains three aspects of theoretical and experimental investigation. Firstly, the heat transfer property of femtosecond laser induced nano-structures, and the heat exchange properties between the surfaces with the nano-structures and the multi-phase flow. Numerical model will be set up to study the physical mechanism. Secondly, the modulation mechanism of the nano-structures to the boiling effect of the multi-phase materials. Thirdly, the effect of the nano-structures to the liquid-solid phase change materials.

多相流传热作为新兴技术具有传热热流密度大、换热效率高和控温精度高等特点，并逐渐应用到大型数据中心高效换热制冷、体积受限的飞行器载荷制冷和高能激光换热制冷等场合中。为了提高多相流的换热性能、调制其相变状态，近年来研究者们在与相变材料相接触的表面制作十微米至百微米量级的微结构。而为了更加深入地对该目标进行研究，本项目将采用不同参数的飞秒激光在材料表面制作纳米周期结构，并研究该纳米周期结构对多相流传热的增强效应。本项目将飞秒激光微纳加工技术应用到换热制冷领域，尚属国际首次，其性质属于结合先进加工技术与换热制冷技术的交叉学科。具体来说，本项目将分别从以下三个方面进行理论和实验研究：第一，纳米波纹结构的传热特性，以及携带纳米波纹结构的表面与多相流的换热特性，建立数值模型对其物理机制进行计算分析；第二，纳米波纹结构对多相流沸腾状态的调控机制；第三。纳米波纹结构对固液相变材料相变特性的影响。

多相流传热作为新兴技术具有传热流密度大、换热效率高和控温精度高等特点，并逐渐应用到大型数据中心的高效换热制冷、体积受限的飞行器载荷制冷和高能激光换热制冷等场合之中。为了提高多相流的换热性能、调制其相变状态，近年来研究者们在与相变材料相接触的表面制作十微米至百微米量级的微结构。而为了更加深入地对该目标进行研究，本项目将采用不同参数的飞秒激光在材料表面制作纳米周期结构，并对该纳米周期结构对多相流传热的增强效应进行研究。. 本项目主要研究了以下内容：第一、喷雾冷却理论模型；第二、喷雾冷却实验平台；第三、多相流喷雾冷却激光器。. 本项目获得了以下结果：第一、建立了喷雾冷却理论模型，可以理论预测在不同喷雾条件下的表面换热系数，有效减少了实验迭代次数和实验周期；第二、建立了喷雾冷却实验平台，通过该实验平台可以方便的测试不同表面样品的表换换热系数，通过实验，飞秒刻蚀表面样品的表面换热系数比平面样品的表面换热系数提升了1倍以上，飞秒刻蚀表面有效提升了表换换热性能；第三、通过3D打印的导热蜂窝结构作为换热媒介，实现了雾化氟利昂和激光器热源之间的换热，这为轻量化小型化激光器的设计提供了思路。