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Effect of magnetic field on laminar convective heat transfer of magnetite nanofluids

机译:磁场对磁铁矿纳米流体层流对流换热的影响

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摘要

The effect of an external magnetic field on the convective heat transfer and pressure drop of magnetite nanofluids under laminar flow regime conditions(Re < 830)is investigated. Specifically, the influence of magnetic field strength and uniformity on the convective heat transfer coefficient is examined through experiments and supporting simulations of the magnetic flux density distribution and magnetic force acting on nanoparticles. The data show that large enhancement in the local heat transfer coefficient can be achieved by increasing the magnetic field strength and gradient. The convective heat transfer enhancement becomes more pronounced at higher Reynolds numbers, with a four-fold enhancement(i.e., relative to the case with no magnetic field)obtained at Re = 745 and magnetic field gradient of 32.5 mT/mm. The effect of the magnetic field on the pressure drop is not as significant. The pressure drop increases only by up to 7.5% when magnetic field intensity of 430 mT and gradients between 8.6 and 32.5 mT/mm are applied. Based on the simulation results of magnetic field and magnetic force distribution, the mechanisms for heat transfer enhancement are postulated to be accumulation of particles near the magnets(leading to higher thermal conductivity locally), and formation of aggregates acting enhancing momentum and enerev transfer in the flow.
机译:研究了外部磁场对层流状态(Re <830)条件下磁铁矿纳米流体对流换热和压降的影响。具体而言,通过实验和对作用在纳米颗粒上的磁通量密度分布和磁力的支持模拟,研究了磁场强度和均匀性对对流传热系数的影响。数据表明,可以通过增加磁场强度和梯度来实现局部传热系数的大幅提高。在较高的雷诺数下,对流传热增强变得更加明显,在Re = 745且磁场梯度为32.5 mT / mm时获得了四倍增强(即,相对于没有磁场的情况)。磁场对压降的影响并不明显。当施加430 mT的磁场强度和8.6至32.5 mT / mm的梯度时,压降最多只能增加7.5%。根据磁场和磁力分布的模拟结果,推测传热增强的机制是磁体附近的颗粒堆积(局部导致较高的导热系数),并在传热过程中形成了增强动量和能传递的聚集体。流。

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  • 作者单位

    Center for Energy, Chemical Engineering Department, The University of Newcastle, Callaghan, NSW 2308, Australia,Nuclear Science and Engineering Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;

    Center for Advanced Particle Processing, Chemical Engineering Department, The University of Newcastle, Callaghan, NSW 2308, Australia;

    Nuclear Science and Engineering Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;

    Nuclear Science and Engineering Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;

    Nuclear Reactor Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;

    Center for Energy, Chemical Engineering Department, The University of Newcastle, Callaghan, NSW 2308, Australia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Magnetite nanofluid; Thermal conductivity; Convective heat transfer coefficient; Laminar flow; Magnetic field; Aggregation;

    机译:磁铁矿纳米流体;导热系数;对流换热系数;层流磁场;聚合;

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