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Magnetic effect on thermo-fluid-dynamics of two-layered fluid systems: Simulations and experiments.

机译：电磁对两层流体系统的热流体动力学的影响：模拟和实验。

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摘要

Fluid dynamics and heat transfer of two-layered immiscible fluid systems is of great importance in a variety of industrial as well as space-exploration applications. Control and optimization of convective thermo-fluid-dynamics of such systems need a complete understanding of all phenomena, especially those induced by surface tension at the fluid interface. The present work is focused on convective flow and heat transfer in a cavity heated from the sides, which is subject to both buoyancy and thermocapillary effects in addition to the influence of magnetic field applied for flow control. With the encapsulant liquid posing magnetic properties, a magnetic force can arise to either enhance or reverse the gravity effect when the cavity is placed in a non-uniform magnetic field. The driving force exploited in the present study is based on the change of magnetic susceptibility of a magnetic material and thus it does not reduce as the system flow reduces unlike the approaches employing the Lorentz's force.; This study is based on two nondimensional schemes. The effects of the fundamental parameters on the thermo-fluid-dynamics and the interfacial shape of the system have been analyzed. The investigation reveals that the Marangoni convection can significantly influence the velocity distribution in the cavity. It also shows that introduction of a magnetic field can easily promote or hinder the Marangoni effect, that is, to further increase or decrease the global convective motion. The effect of the magnetic body force of the upper magnetic fluid has a difficulty to penetrate through the interface of the two fluids, so care must be taken in selecting the geometry and the fluids with proper characteristics when optimizing the system for industrial applications. It has been shown that the interfacial velocity can be altered as much as 100% and that even a small change in the velocity field can produce significant changes in temperature distribution. This in turn affects the local Nusselt number and thus the global heat transfer reducing it or enhancing it by up to 100%.; Results of the experiments and comparison with numerical calculations are also provided. The theoretical-numerical and experimental results are in good qualitative agreement, thus confirming the feasibility of using magnetic fluid and magnetic field to control the thermo-fluid-dynamics of two-layered fluid systems.
机译：两层不混溶流体系统的流体动力学和热传递在各种工业和空间探索应用中都非常重要。这种系统的对流热流体动力学的控制和优化需要全面了解所有现象，尤其是流体界面处的表面张力引起的现象。目前的工作集中在从侧面加热的空腔中的对流和热传递，除了用于流动控制的磁场的影响外，它还具有浮力和热毛细作用。当密封剂液体具有磁性时，当空腔置于非均匀磁场中时，会产生磁力以增强或逆转重力效应。本研究中利用的驱动力是基于磁性材料的磁化率的变化，因此，与采用洛伦兹力的方法不同，它不会随着系统流量的减少而减小。这项研究基于两个无量纲的方案。分析了基本参数对系统的热流体动力学和界面形状的影响。研究表明，Marangoni对流会显着影响空腔中的速度分布。它还表明，磁场的引入可以容易地促进或阻碍Marangoni效应，即进一步增加或减少整体对流运动。上层磁性流体的磁力的作用很难穿透两种流体的界面，因此在优化用于工业应用的系统时，必须谨慎选择几何形状和具有适当特性的流体。已经表明，界面速度可以改变多达100％，并且即使速度场的很小变化也可以产生温度分布的显着变化。反过来，这会影响本地的Nusselt数，从而影响全球热量传递，从而使Nusselt数减少或增加100％。还提供了实验结果并与数值计算进行了比较。理论数值与实验结果吻合良好，从而证实了利用磁流体和磁场控制两层流体系统热流体动力学的可行性。

著录项

  • 作者

    Ludovisi, Daniele.;

  • 作者单位

    University of Illinois at Chicago.;

  • 授予单位 University of Illinois at Chicago.;
  • 学科 Engineering Mechanical.; Physics Electricity and Magnetism.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 275 p.
  • 总页数 275
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;电磁学、电动力学;工程材料学;
  • 关键词

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