Qin Feifei, Zhao Jianlin, Kang Qinjun, Brunschwiler Thomas, Derome Dominique, Carmeliet Jan
Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zürich (Swiss Federal Institute of Technology in Zürich), Zürich 8092, Switzerland.
Laboratory of Multiscale Studies in Building Physics, Empa (Swiss Federal Laboratories for Materials Science and Technology), Dübendorf 8600, Switzerland.
Phys Rev E. 2021 Feb;103(2-1):023311. doi: 10.1103/PhysRevE.103.023311.
Drying of colloidal suspension towards the exploitation of the resultant nanoparticle deposition has been applied in different research and engineering fields. Recent experimental studies have shown that neck-based thermal structure (NTS) by colloidal nanoparticle deposition between microsize filler particle configuration (FPC) can significantly enhance vertical heat conduction in innovative three-dimensional chip stacks [Brunschwiler et al., J. Electron. Packag. 138, 041009 (2016)10.1115/1.4034927]. However, an in-depth understanding of the mechanisms of colloidal liquid drying, neck formation, and their influence on heat conduction is still lacking. In this paper, using the lattice Boltzmann method, we model neck formation in FPCs and evaluate the thermal performances of resultant NTSs. The colloidal liquid is found drying continuously from the periphery of the microstructure to its center with a decreasing drying rate. With drying, more necks of smaller size are formed between adjacent filler particles, while fewer necks of larger size are formed between filler particle and the top/bottom plate of the FPCs. The necks, forming critical throats between the filler particles, are found to improve the heat flux significantly, leading to an overall heat conduction enhancement of 2.4 times. In addition, the neck count, size, and distribution as well as the thermal performance of NTSs are found to be similar for three different FPCs at a constant filler particle volume fraction. Our simulation results on neck formation and thermal performances of NTSs are in good agreement with experimental results. This demonstrates that the current lattice Boltzmann models are accurate in modeling drying of colloidal suspension and heat conduction in microporous structures, and have high potentials to study other problems such as surface coating, salt transport, salt crystallization, and food preserving.
通过胶体悬浮液干燥来利用所得纳米颗粒沉积的方法已应用于不同的研究和工程领域。最近的实验研究表明，在微尺寸填料颗粒构型（FPC）之间通过胶体纳米颗粒沉积形成的颈部基热结构（NTS）可以显著增强创新型三维芯片堆栈中的垂直热传导[Brunschwiler等人，《电子封装杂志》138, 041009 (2016)10.1115/1.4034927]。然而，目前仍缺乏对胶体液体干燥、颈部形成机制及其对热传导影响的深入理解。在本文中，我们使用格子玻尔兹曼方法对FPC中的颈部形成进行建模，并评估所得NTS的热性能。发现胶体液体从微观结构的外围向其中心持续干燥，干燥速率逐渐降低。随着干燥过程的进行，相邻填料颗粒之间形成更多尺寸较小的颈部，而填料颗粒与FPC的顶板/底板之间形成的尺寸较大的颈部较少。这些颈部在填料颗粒之间形成关键的通道，被发现能显著提高热通量，导致整体热传导增强2.4倍。此外，发现在恒定的填料颗粒体积分数下，三种不同的FPC的颈部数量、尺寸、分布以及NTS的热性能相似。我们关于NTS颈部形成和热性能的模拟结果与实验结果吻合良好。这表明当前的格子玻尔兹曼模型在模拟胶体悬浮液干燥和微孔结构中的热传导方面是准确的，并且在研究其他问题如表面涂层、盐分传输、盐结晶和食品保鲜等方面具有很大潜力。
