In a flow battery, the salient impact of the electrolyte velocity on the mass transfer coefficient in carbon felt electrodes is demonstrated and quantified. A lab-scale flow battery, fed with identical electrolyte solutions containing Fe²⁺/Fe³⁺ as active substances in both the anode and the cathode, is used to realize stable tests free from side reactions in a broad range of current densities. The electrolyte velocities ranging from 2.5 to 15 mm s⁻¹ are selected in this work, which are typical in flow through electrodes in most flow batteries. By measuring limiting currents at various flow rates, a correlation between the mass transfer coefficient and the velocity in dimensionless form is obtained as Sh = 1.68 Re^0.9. Meanwhile, a 2-D numerical model incorporating this correlation and the experimentally measured electrolyte conductivity is proposed. Voltage losses of the battery fed with adequate reactants at different velocities are both experimentally measured and numerically simulated. The agreement between simulated results and experimental data verifies the applicability of this correlation under normal operating conditions below limiting currents.

中文翻译：

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传质系数对碳毡电极中电解质速度的依赖性：确定与验证

在液流电池中，电解质速度对碳毡电极中传质系数的显着影响得到了证明和量化。在实验室规模的液流电池中，在阳极和阴极中均^填充有相同的含有Fe ²⁺ / Fe ³⁺作为活性物质的电解质溶液，可用于在宽范围的电流密度下实现无副反应的稳定测试。在这项工作中，电解质速度的选择范围是2.5到15 mm s ^-1，这是大多数液流电池中流经电极的典型现象。通过测量各种流速下的极限电流，可以得到无量纲形式的传质系数与速度之间的相关性，Sh = 1.68 Re^0.9。同时，提出了一种二维数值模型，该模型结合了这种相关性和实验测量的电解质电导率。既以实验方式又以数值方式模拟了以不同速度注入适当反应物的电池的电压损失。仿真结果与实验数据之间的一致性验证了这种相关性在极限电流以下的正常工作条件下的适用性。