Experimental determination of the critical Rayleigh number for thermomagnetic convection with focus on fluid composition
Experimental determination of the critical Rayleigh number for thermomagnetic convection with focus on fluid composition
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DOI：
10.1016/j.jmmm.2015.01.014
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发表时间：
2015-05
影响因子：
2.7
通讯作者：
M. Heckert;Lisa Sprenger;A. Lange;S. Odenbach
中科院分区：
文献类型：
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作者：
M. Heckert;Lisa Sprenger;A. Lange;S. Odenbach
研究了两种基于煤油的磁流体（EMG 905和NF4000C）的热磁对流，重点是确定流体层中对流不稳定发生的临界瑞利数。通过与已发表的酯基APG 513a流体数据和理论预测数据的比较，发现EMG和APG流体在Ra m， c≈2500附近的临界磁瑞利数相似，接近期望值，但nf流体的Ra m， c= 856。由于后者与其他两种流体的主要区别在于粒径分布，因此假设粒径对磁流体的对流行为具有重要的但尚未研究的影响。
Thermomagnetic convection has been investigated for two kerosene-based magnetic fluids (EMG 905 and NF4000C) with a focus on the determination of the critical Rayleigh numbers for the onset of convective instability in a fluid layer. A comparison with published data for the ester-based APG 513A-fluid and theoretical predictions yield similar critical magnetic Rayleigh numbers for the EMG and APG-fluids around Ra m, c≈ 2500, which is near the expected value, but Ra m, c= 856 for the NF-fluid. As the latter differs from the other two fluids mainly in the particle size distribution, it is assumed that the size of the particles has an important and yet uninvestigated impact on the convective behavior of magnetic fluids.