Effective thermal conductivity of dispersions with a liquid continuous phase

液体连续相分散体的有效导热率

• 批准号: 463473804
• 负责人: Professor Dr.-Ing. Andreas Paul Fröba
• 金额: --
• 依托单位: Erlangen Graduate School in Advanced Optical Technologies (SAOT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/463473804?language=en
• 关键词: Effective; thermal; conductivity; dispersions; liquid

Dispersions with a liquid continuous phase are heterogeneous systems which consist of a liquid dispersion medium and a dispersed phase of colloidal particles. These particles can be solid particles as given in nanofluids, liquid particles, i.e. droplets forming emulsions, or gaseous particles in the form of bubbles which are present in foams. A key property characterizing dispersions is their effective thermal conductivity (ETC). Many literature studies report that by adding a small amount of solid nanoparticles to liquids, the ETC of nanofluids can be increased extraordinarily relative to the base fluid, while others do not observe any significant enhancement. Until today, debate has continued on the relevant mechanisms affecting the effective thermal conduction in nanofluids where Brownian motion, interfacial layering, and aggregation related to the particles or a combination of such effects are considered. This is reflected in related modeling approaches for the ETC of nanofluids providing often strong variations in the predicted values. The ongoing controversy about the ETC of dispersions is also connected to the reliability of the experimental methods. The main objective of the present project is to contribute to a fundamental understanding of the ETC of dispersions with a liquid continuous phase. For that, the relevant influences should be investigated systematically. Here, the focus lies on the thermal conductivities of the dispersed and the continuous phase, the morphology of the dispersed particles, and particle aggregation. Furthermore, conclusions about the roles of an interfacial thermal resistance and of Brownian motion of the particles regarding the ETC should be drawn. For addressing these effects, selected dispersions of solid or liquid particles on the nanometer scale in a liquid continuous phase with different physical and chemical characteristics should be investigated theoretically and experimentally by using a steady-state guarded parallel-plate instrument. Together with critically evaluated literature data, the experimental results should serve as a reliable database for studying the aforementioned influences on the ETC of such systems. They should also help to answer the question whether the findings obtained for dispersions with solid particles are transferable to those with liquid particles. For the characterization of the dispersions with respect to particle size and shape as essential parameters for the ETC, information about the translational and rotational diffusivity of the particles should be accessed by dynamic light scattering. Based on the experimental results, theoretical considerations, and exisiting modelling approaches, a generalized prediction method for the ETC of dispersions with a liquid continuous phase should be developed.

具有液体连续相的分散体是由液体分散介质和胶体颗粒的分散相组成的非均相系统。这些颗粒可以是纳米流体中给出的固体颗粒、液体颗粒（即形成乳液的液滴）或泡沫中存在的气泡形式的气体颗粒。分散体的一个关键特性是其有效导热系数（ETC）。许多文献研究报道，通过向液体中添加少量固体纳米颗粒，纳米流体的ETC相对于基础流体可以显著增加，而其他文献没有观察到任何显著的增强。直到今天，辩论仍在继续的相关机制，影响有效的热传导的纳米流体中的布朗运动，界面分层，并聚集有关的颗粒或这些效果的组合被认为是。这反映在用于纳米流体的ETC的相关建模方法中，所述方法通常提供预测值的强烈变化。关于色散ETC的持续争论也与实验方法的可靠性有关。本项目的主要目标是促进对具有液体连续相的分散体的ETC的基本理解。为此，应系统地研究相关影响。在这里，重点在于分散相和连续相的热导率，分散颗粒的形态，和颗粒聚集。此外，界面热阻和颗粒的布朗运动关于ETC的作用的结论应该得出。为了解决这些影响，选定的分散体的固体或液体颗粒在纳米尺度上的液体连续相具有不同的物理和化学特性，应进行理论和实验研究，通过使用稳态防护平行板仪器。连同严格评估的文献数据，实验结果应作为一个可靠的数据库，用于研究上述影响的ETC的这种系统。它们还应有助于回答这样一个问题，即从含有固体颗粒的分散体中获得的结果是否可转移到含有液体颗粒的分散体中。对于分散体的表征相对于颗粒尺寸和形状作为ETC的基本参数，关于颗粒的平移和旋转扩散率的信息应通过动态光散射来访问。基于实验结果，理论上的考虑，和建模方法，一个广义的预测方法的ETC的分散液与液体连续相应开发。