制冷剂与润滑油溶析交变过程中纳米粒子的迁移机制

In order to utilize nano-refrigerant to improve the efficiency of refrigeration system, it is necessary to know whether the nanoparticles can cycle continuously and stably in refrigeration system, and the key issue is to understand the nanoparticle migration characteristics between lubricating oil and refrigerant during the refrigerant-oil alternating process of dissolution and separation. The project applies experiment and theoretical analysis, to investigate the nanoparticle migration mechanisms between refrigerant and lubricating oil during the alternating process of dissolution and separation caused by the phase change of refrigerant, and to propose a quantitative description method. The condensation morphological characteristics of vapor-phase refrigerant during the process of condensation and dissolution with lubricating oil, and the formation and breakage morphological characteristics of bubble during the process of vaporization and separation from the lubricating oil, are known by visualization experiments. The migration mass of nanoparticle is indirectly obtained by light transmission method, and then the relationship between the migration mass and the related influence factors are concluded. The motion models of spherical nanoparticle and carbon nanotube in liquid are established using Lagrange method and lattice Boltzmann method. The motion models of nanoparticle in vapor are established based on bubble dynamics, theory of air flotation and particle capture theory. The project provides theory basis for the cycle characteristics of nanoparticle in refrigeration system and the stable running of refrigeration system using nano-refrigerant.

为了应用纳米制冷剂以提高制冷系统能效，必须知道纳米粒子能否在制冷系统中连续稳定地循环，其关键是要了解制冷剂与润滑油的溶解与析出交互变化过程中纳米粒子在润滑油和制冷剂之间的迁移特性。本项目采用实验与理论分析相结合的方法，探究在制冷剂相变导致的制冷剂与润滑油溶析交变过程中，纳米粒子在制冷剂与润滑油这二种流体间迁移的机制，并提出定量描述方法。通过可视化实验，了解气相制冷剂冷凝并与润滑油溶解的过程中的凝结形态特征，以及制冷剂蒸发而从润滑油中析出过程中的气泡形成及破裂的形态特征；通过光透法间接测得纳米粒子的迁移量，并总结迁移量与影响因素间的关系；基于拉格朗日方法和格子波尔兹曼方法分别建立球形纳米粒子和碳纳米管在液态流体中的运动模型；基于气泡动力学、气浮理论和颗粒捕集理论，建立纳米粒子在气液间迁移时的运动模型。为确定纳米粒子在制冷系统中的循环特性、保证应用纳米制冷剂的制冷系统的运行稳定提供理论依据。

为了应用纳米制冷剂以提高制冷系统能效，必须知道纳米粒子能否在制冷系统中连续稳定地循环，其关键是要了解制冷剂与润滑油的溶解与析出交互变化过程中纳米粒子在润滑油和制冷剂之间的迁移特性。对此，我们设计并搭建了可模拟含油纳米制冷剂溶析交变的可视化实验装置，同时提出了定量评估纳米粒子迁移特性的实验方法。通过实验，我们得到了溶析交变下纳米粒子的迁移规律，分析并提出了其迁移机制，并建立了预测模型。在此基础上，我们针对影响纳米粒子迁移的关键问题——粒子团聚进行了实验、理论研究。我们设计了基于动态光散射的表征方法，通过测量含油纳米制冷剂中纳米粒子尺寸的动态变化来表征纳米粒子的团聚特性，并建立了纳米粒子在含油纳米制冷剂中的团聚模型。我们超额完成了研究计划，取得了一系列创新成果。至今共发表论文17篇，其中9篇被SCI收录，论文被SCI他引35次。此外，获得1项中国发明专利授权。本研究为评估纳米粒子在制冷系统中的循环特性提供了理论依据，促进了纳米流体技术的应用进程。