Thermal Rayleigh-Marangoni convection in a three-layer liquid-metal-battery model
Thermal Rayleigh-Marangoni convection in a three-layer liquid-metal-battery model
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DOI：
10.1103/physreve.95.053114
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发表时间：
2017-05-25
影响因子：
2.4
通讯作者：
Schumacher, Joeg
中科院分区：
文献类型：
--
作者：
Koellner, Thomas;Boeck, Thomas;Schumacher, Joeg
在一个简化的三层液态金属电池（LMB）模型中，研究了浮力驱动的Rayleigh-Benard对流（RC）和表面张力驱动的Marangoni对流（MC）的联合作用.三层模型由液态金属合金阴极、熔盐隔离层和顶部的液态金属阳极组成。对流由热电解质和较冷电极之间的温度梯度触发，这是操作期间电阻热释放的结果。我们提出了一个纯热传导状态的线性稳定性分析，结合三维直接数值模拟的非线性湍流演化的基础上的伪谱方法。五种不同的对流模式被确定在配置中，这是部分地相互耦合：RC在上电极，RC与内部加热的熔盐层，和MC在熔盐和电极之间的界面，以及在中间层和下电极的反对流。线性稳定性分析证实，在本设置中的附加马兰戈尼效应增加了线性不稳定模式的增长率，即，Marangoni不稳定性和Rayleigh-Benard不稳定性在熔盐层中共同作用。临界Grashof数和Marangoni数随中间层厚度的增加而减小。对流的发病计算阈值被发现为现实的电流密度的实验室大小的LMB。全球湍流传热遵循缩放预测内部加热RC。在经典Rayleigh-Benard情况下，全球湍流动量传递与湍流对流相当。总之，我们的研究表明，将马兰戈尼效应产生更小的流动结构，改变速度的大小，并提高了整个三层结构的湍流传热。
The combined effects of buoyancy-driven Rayleigh-Benard convection (RC) and surface tension-driven Marangoni convection (MC) are studied in a triple-layer configuration which serves as a simplified model for a liquidmetal battery (LMB). The three-layer model consists of a liquidmetal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Convection is triggered by the temperature gradient between the hot electrolyte and the colder electrodes, which is a consequence of the release of resistive heat during operation. We present a linear stability analysis of the state of pure thermal conduction in combination with three-dimensional direct numerical simulations of the nonlinear turbulent evolution on the basis of a pseudospectral method. Five different modes of convection are identified in the configuration, which are partly coupled to each other: RC in the upper electrode, RC with internal heating in the molten salt layer, and MC at both interfaces between molten salt and electrode as well as anticonvection in the middle layer and lower electrode. The linear stability analysis confirms that the additional Marangoni effect in the present setup increases the growth rates of the linearly unstable modes, i.e., Marangoni and Rayleigh-Benard instability act together in the molten salt layer. The critical Grashof and Marangoni numbers decrease with increasing middle layer thickness. The calculated thresholds for the onset of convection are found for realistic current densities of laboratory-sized LMBs. The global turbulent heat transfer follows scaling predictions for internally heated RC. The global turbulent momentum transfer is comparable with turbulent convection in the classical Rayleigh-Benard case. In summary, our studies show that incorporating Marangoni effects generates smaller flow structures, alters the velocity magnitudes, and enhances the turbulent heat transfer across the triple-layer configuration.