液-液相分离工质在微通道内多相流动传热特性及分离过程调控机制

Microchannel heat sink is widely used in the heat dissipation of micro devices in advanced engineering fields such as microelectronics, energy, aerospace and nuclear energy technologies. The liquid-liquid phase separation solution with a lower critical separation temperature (LCST) has great potential in improving the heat transfer performance of the microchannel heat sink, reducing the channel pressure drop and avoiding system vibration. This project will focus on the multiphase heat and mass transport mechanism under the coupling effects of liquid-liquid phase separation, flow and heat transfer processes in microchannels. The research work is gradually carried out from the liquid-liquid phase separation process, flow and heat transfer characteristics of solution in the microchannel and heat transfer enhancement of the heat sink. Firstly, the heat and mass transfer mechanism of multiphase during the solute precipitation, growth and coalescence in the static state will be obtained. Subsequently, the coupling mechanism of liquid-liquid phase separation, flow and heat transfer processes in microchannels will be investigated. Then, the prediction correlation of heat transfer coefficient and pressure drop in the microchannel will be proposed. Thereafter, a new micro-rib structure for regulating the liquid-liquid phase separation process, enhancing the local disturbances and expanding the heat transfer area will be developed. Eventually, a method for strengthening the heat transfer performance of microchannel heat sink which based on regulation of liquid-liquid phase separation process will be proposed. These studies will accelerate the development of micro-cooling equipment.

微通道热沉广泛应用于微电子技术、能源动力、航天航空和核能技术等领域中微型器件的散热。具有下临界分离温度（LCST）的液-液相分离溶液在提高微通道热沉传热性能，降低通道压降，避免系统振动等方面具有极大的潜力。本项目将重点针对微通道内LCST溶液相分离与流动传热过程耦合作用下复杂多相能质传输机制，从液-液相分离过程、溶液在微通道内的流动传热特性和微通道热沉传热性能强化这三个方面逐步展开研究工作。首先，揭示静态时溶质析出、生长及聚并过程中的多相能质传输机理；随后，探明微通道内液-液相分离与流动传热过程的耦合作用机制，提出适用于斯宾那多和形核分离过程的微通道壁面传热系数和压降预测关联式；在此基础上，开发调控微通道内液-液相分离过程、增强局部扰动和扩展传热面积的新型微肋结构，提出基于液-液相分离过程调控的微通道热沉传热性能强化方法，从而加速微型冷却设备的研发。

微通道热沉广泛应用于微电子技术、能源动力、航天航空和核能技术等领域中电子器件的散热，但随着芯片集成化、微型化的发展，现有技术难以胜任高功率、多热点、变工况电子器件的控温需求。本项目在微通道热沉中引入具有下临界分离温度（LCST）的液-液相分离溶液，以期提高微通道热沉传热性能，降低通道压降，避免系统振动。项目内容研究进展如下：构建了液-液相分离过程的分子动力学模型，探明了温度和质量分数对氢键缔结、分子团簇当量直径以及团聚强度的影响规律，证实一定的分子团簇大小和团聚强度是发生液-液相分离的必要条件，搭建了液-液相分离过程微观可视化实验平台，揭示了静态时液-液相分离过程中溶质析出、生长及聚并过程中复杂多相能质传输机理；搭建了微通道内液-液相分离过程的可视化实验研究平台，探索了扩散和自然对流驱动下的液-液相分离机制，提出了不同驱动力条件下分离速率等相分离行为的预测关联式，明晰了溶液质量分数等参数对相分离溶液在微通道内对流换热系数的影响规律；构建了3D-IC层间微通道热-流-固耦合模型，证实三乙胺溶液可将芯片最高温度降低20K，探明了相分离温度区间等参数对3D-IC自适应控温特性的影响，开发了调控液-液相分离过程的层间微通道结构优化方法，实现了多热点、高功率芯片动态运行时的有效控温。在圆满完成项目内容的前提下，拓展研究了导热和自然对流对PCM相变换热过程的影响，提出了适用于有机相变工质的自然对流作用权重预测关系式；构建了填充石蜡/In-Sn-Bi合金组合PCM的相变储热式热沉，验证了组合PCM协同强化导热和自然对流的可行性，提出了PCM热沉对电子器件有效保护时间的预测关系式；将液-液相分离工质与PCM结合，有效缓解了高功率、多热点芯片动态运行时温度分布的时空不均匀性，为电子器件热管理系统的设计提供了理论依据，助力攻克受限空间内超高功率电子器件的控温难题。