The successful use of clean energy sources will rest, in part, on the availability of efficient energy storage systems. Thus, the present work examines two critical factors (flow patterns and residence time distribution, RTD) affecting the performance of one of the most promising energy storage systems: redox flow batteries (RFBs). The goal is to develop a methodology for analyzing the hydrodynamic and mass transport behavior within a commercial redox flow battery (CRFB). This methodology includes modeling of the flow behavior as well as its experimental validation with RTD. The CRFB consisted of a square geometry with an interdigitated flow field design. Experimental residence time distribution curves for this device were obtained at four different flow rates using the stimulus-response technique with step signal. Theoretically, the flow behavior within the CRFB was approximated by an axial dispersion model (ADM), and a plug dispersion exchange model (PDE), as well as by solving the hydrodynamic equations (Navier–Stokes and Brinkman equations) and the mass transport equation (convection-diffusion) using COMSOL Multiphysics® 5.3. The calculated RTD curves are in good agreement with the experimental RTD curves.

Our theoretical and experimental analysis resulted in better approximations of the axial dispersion, and the presence of stagnant zones, and channeling and by-pass (i.e., preferential flow) effects at low and intermediate Reynolds numbers (Re). The experimental RTD curves show that the liquid flow pattern in the CRFB deviates considerably from the axial dispersion model at low Re, conditions under which the CRFB exhibits significant channeling effects, as well as stagnant and dead zones. The PDE model was able to describe the deviation from ideal flow pattern caused by channeling, recycling, or by the presence of stagnant regions in the CRFB. The mass transport in the CRFB was determined by measuring the distribution of tracer molecules at different time points after the initial (step) tracer injection. The interdigitated flow field geometry exhibited a homogeneous flow distribution, featuring an increased mean electrolyte velocity inside the electrode. This simulation allowed locating stagnant zones that would locally affect the mass transport properties and globally lead to a reduction of the RFB conversion efficiency.

清洁能源的成功使用将部分取决于有效储能系统的可用性。因此，本工作研究了影响最有前途的储能系统之一的性能的两个关键因素（流动模式和停留时间分布，RTD）：氧化还原液流电池（RFB）。目标是开发一种用于分析商用氧化还原液流电池（CRFB）内的流体动力学和传质行为的方法。该方法学包括流动行为的建模以及使用RTD进行的实验验证。CRFB由具有交叉指状流场设计的方形几何形状组成。使用带有阶跃信号的刺激响应技术，在四个不同的流速下获得了该设备的实验停留时间分布曲线。从理论上讲 CRFB中的流动行为通过轴向扩散模型（ADM）和塞子扩散交换模型（PDE）以及通过求解流体力学方程（Navier–Stokes和Brinkman方程）和质量输运方程（对流）来近似-扩散）使用COMSOLMultiphysics®5.3。计算得出的RTD曲线与实验RTD曲线非常吻合。

我们的理论和实验分析得出了更好的近似轴向弥散，停滞区的存在以及在中低雷诺数（Re）下的窜流和旁通（即优先流动）效应。RTD实验曲线表明，在低Re的条件下，CRFB中的液体流动模式与轴向弥散模型有很大的偏离，在该条件下CRFB表现出显着的通道效应以及停滞和死区。PDE模型能够描述由于通道，再循环或CRFB中停滞区域而导致的与理想流型的偏差。通过测量初始（逐步）示踪剂注入后不同时间点的示踪剂分子分布，可以确定CRFB中的质量传递。相互交叉的流场几何形状表现出均匀的流动分布，其特征在于电极内部的平均电解质速度增加。该模拟允许定位停滞区域，该停滞区域将局部影响传质特性并总体上导致RFB转换效率降低。