Newsletter  2021.3  Index

Theme : "The Conference of Fluid Engineering Division (March issue)” Preface (T. HASHIMOTO，S. MATSUDA，H.J. PARK) Direct Numerical Simulation and Linear Processes of Stably Stratified Sheared Turbulence Aoi NAKAMURA, Shinya OKINO and Hideshi HANAZAKI (Kyoto University) Synthesis of microcapsules containing temperature-sensitive magnetic particles and understanding of flow characteristics Kazuki OGURA, Keiko ISHII and Koji FUMOTO (Aoyama Gakuin University) Flight simulation game of micro air vehicle Yoshitaka ISODA , Takuma SADANAGA , Makoto KAWANO (Kyoto Institute of Technology) Meisei Tennyo, Dance in the Air! Atsuki FUKUHARA (Meisei University)

 

Synthesis of microcapsules containing temperature-sensitive magnetic particles and understanding of flow characteristics

Kazuki OGURA Aoyama Gakuin University	Keiko ISHII Aoyama Gakuin University	Koji FUMOTO Aoyama Gakuin University

Abstract

This research aimed at the practical application of a heat transport device that does not require an external power source by utilizing the unique property of temperature-sensitive magnetic fluid having magnetic susceptibility to temperature. Although magnetic fluid has high heat transport performance, it forms a chain structure called a “cluster” under the magnetic field and causes blockage of a channel. However, it is difficult to visualize the magnetic fluid because it is black opaque and the dispersed magnetic particles are extremely small. Therefore, the state of the magnetic fluid flow has not been well known and the cluster control techniques have not been established. By controlling this cluster, magnetic fluid devices will be further developed. Therefore, a fluid simulating a magnetic fluid was created by using microencapsulation method. The advantage of encapsulation is that the particle size can be increased while controlling the magnetism of each capsule. Further, by encapsulating a fluorescent dye together with the magnetic particles, a fluorescence labeled, visible magnetic microcapsule can be produced. Understanding the cluster dynamics, the cluster structure could be controlled by flow conditions and temperature conditions in a capillary tube. Therefore, this study evaluated the cluster formation characteristics under various conditions quantitatively. In this report, we focused on the effects of shearing force, magnetic field strength, and heat on the cluster length in forced convection field by visualizing the magnetic microcapsules. As a result, some conditions affecting cluster formation and the cluster formation process were clarified. The length of the cluster increased as the fluid shear force increased, and the length decreased as magnetic flux density decrease. In addition, by applying heat to the channel, the magnetization of the magnetic particles contained in the capsule was reduced and cluster length was shortened. It is conceivable that the prepared magnetic microcapsules had the same characteristics of the conventional temperature-sensitive magnetic fluid.

Key words

 Temperature-sensitive magnetic particle, Magnetic microcapsule, Working fluid, Microencapsulation

Figures

Figure1　 Outline of the measurement system.

Figure2　 Image of cluster length over time .