Optical visualization of the formation behavior of magnetic particle clusters in a forced convection field
Optical visualization of the formation behavior of magnetic particle clusters in a forced convection field
复制标题
强制对流场中磁性粒子簇形成行为的光学可视化
DOI：
10.1016/j.jmmm.2022.169433
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发表时间：
2022
影响因子：
2.7
通讯作者：
Koji Fumoto
中科院分区：
文献类型：
--
作者：
Keiko Ishii;Kazuki Ogura;Koji Fumoto
温敏磁性流体除了提高流体本身的传热系数外，还有望通过控制悬浮磁性颗粒的内部流动来实现更有效的传热。磁团簇被认为是在施加磁场的情况下在通道内产生的，但是它们的测量在实验上是困难的，并且由于复杂的流动而使用各种假设进行计算。因此，在这项研究中，荧光磁性微胶囊创建可视化集群的形成和崩溃的行为在强制对流场中的磁场应用位置。总体而言，由于流体剪切力，较短的簇倾向于在较大的流速下形成。当流体剪切力超过一定值时，磁性团簇在壁面上坍缩并停止生长。团簇的平均长度在临界剪切力之前的区域变得不稳定。团簇坍缩边界处的剪切应力与外加磁通量有关。团簇的形成行为可以通过流速、磁通密度和颗粒磁化强度来控制。在这项研究中提出的意见，将有助于实现更有效的强制对流传热的磁性流体。
Temperature-sensitive magnetic fluids are expected to achieve more efficient heat transfer by controlling the internal flow of suspended magnetic particles, in addition to improving the heat transfer coefficient of the fluid itself. Magnetic clusters are considered to be generated inside the channel under the application of a magnetic field, but their measurement is difficult experimentally, and various assumptions have been used for calculation because of the complicated flow. Therefore, in this study, fluorescent magnetic microcapsules were created to visualize cluster formation and collapse behavior at the magnetic field application position in the forced convection field. Overall, shorter clusters tended to form at larger flow velocities owing to the fluid shear force. When the fluid shear force applied exceeded a certain level, the magnetic clusters collapsed on the wall surface and stopped growing. The average length of the cluster became unstable in the region immediately before the critical shear force. The shear stress at the boundary where the cluster collapsed was correlated with the applied magnetic flux. The cluster formation behavior can be controlled by the flow velocity, magnetic flux density, and particle magnetization. The observations that would aid the achievement of a more efficient forced convection heat transfer by magnetic fluids are presented in this study.