Magnetothermal force effect on natural convection through a partially-heated vertical channel
Magnetothermal force effect on natural convection through a partially-heated vertical channel
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DOI：
10.1299/jtst.2020jtst0019
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发表时间：
2020
影响因子：
1.2
通讯作者：
Kengo Wada;Hiroaki Fujiwara;M. Kaneda;K. Suga
中科院分区：
文献类型：
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作者：
Kengo Wada;Hiroaki Fujiwara;M. Kaneda;K. Suga
对部分加热的垂直通道中顺磁流体的自然对流进行了数值研究，研究了加热壁后两块磁铁产生的磁场作用。磁铁以相反的方向排列。由于磁极之间的距离较短，这种磁体取向在磁体结合处产生垂直于磁体的强磁力。当磁体附近的壁面加热引起磁化率随温度变化时，在磁体结附近会产生显著的磁热力。这一附加力与沿受热壁的自然对流重叠，导致沿受热壁的热和流体流动的变化。结果表明，在磁体结面高度以下，流动变慢，局部换热受到抑制；在结面高度以上，流动加速和换热增强，其影响依赖于磁体相对于受热壁的相对高度。研究还发现，在特定的磁体高度处发生了向振动流的转变。时间平均的Nusselt数表明，这种振动对流具有显著增强换热的潜力，因为这种由磁感应产生的流动振动沿着加热的壁面一直持续到出口。
Natural convection of a paramagnetic fluid through a partially-heated vertical channel is numerically studied in the presence of a magnetic field from two block magnets placed behind the heated wall. Magnets are aligned with opposite orientations. This magnet orientation induces strong magnetic force normal to the magnet at the magnet junction due to short distance between poles. When the temperature-dependent magnetic susceptibility changes due to wall heating near the magnet, the magnetothermal force is induced remarkably near the magnet junction. This additional force overlaps to the natural convection along the heated wall and results in the changes of heat and fluid flow along the heated wall. It is found that, flow becomes slow and the local heat transfer is suppressed below the elevation of the magnet junction, and the flow acceleration and heat transfer enhancement are observed above the junction elevation, of which effects depend on the relative magnet elevation to the heated wall. It is also found that the transition to vibrating flow occurs at the specific magnet elevation. The timeaveraged Nusselt number suggests this vibrating convection has the potential to enhance the heat transfer remarkably because this magnetically-induced flow vibration continues along the heated wall up to the outlet.