Augmented Mass Transport in Sheared Suspensions

研究综述：本研究旨在提高目前对剪切悬浮液中层流区大分子溶质输运现象的认识。利用多重内反射荧光(MIRF)新技术，强化传质的特征是有效的扩散系数，并使用旋转圆盘流动系统进行测定。测量了几种表征良好的大分子溶质在悬浮液中的扩散系数，它们是悬浮液颗粒体积分数、颗粒尺寸、颗粒刚性、悬浮液粘度/粘弹性和体系剪切速率的函数。实际意义：这项研究可以通过识别和表征重要的实验参数和机理来提高我们目前对剪切悬浮液中强化传质的理解，这些参数和机理涉及到增强大分子溶质在剪切悬浮液中的扩散能力。可受益的化学和生物系统领域包括：1)更好地了解涉及相变(结晶、熔融等)流动的聚合物加工操作。以及分散和分层的多相流；2)更好地设计非等温管式和CSTR反应器、填充床和流化床反应器，以及血液透析器和血液氧合器等体外流动系统；3)更好地了解血栓形成、动脉粥样硬化和溶血等疾病过程。

Research Summary: This research program is aimed at improving current understanding of transport phenomenon of macromolecular solutes in sheared suspensions in the laminar flow regime. Using the novel technique of multiple internal reflection fluorescence (MIRF), augmented mass transfer is characterized by an effective diffusivity and is determined using a rotating disc flow system. The diffusion coefficients of several well characterized macromolecular solutes are measured in aqueous suspensions as a function of suspension particle volume fraction, particle size, particle rigidity, suspension viscosity/viscoelasticity, and system shear rate. Practical Significance: This study could lead to results that improve our current understanding of augmented mass transfer in sheared suspensions by identifying and characterizing the important experimental parameters and mechanisms involved in enhancing the diffusivities of macromolecular solutes in sheared suspensions. Chemical and biological system areas that could benefit include: 1) better understanding of polymer processing operations involving flows with phase change (crystallization, melting, etc.) as well as with dispersed and stratified multiphase flows; 2) better design of nonisothermal tubular and CSTR reactors, packed and fluidized bed reactors, and extracorporeal flow systems such as hemodialyzers and blood oxygenators; and 3) better biomedical understanding of such disease processes as thrombogenesis, atherogenesis, and hemolysis.