【作者】 李婷婷；

【导师】 王家德；

【作者基本信息】 浙江工业大学 ， 环境科学与工程， 2015， 硕士

【摘要】 柱塞流电化学反应器(PFER)是一种可以提高电流效率,降低处理成本的新型电化学法处理技术。网板柱塞流电化学反应器(MPE-PFER)因阴阳电极面积相同且垂直于流体流动方向,电极为棱形网孔结构,可解决传统柱塞流电化学反应器电流分布不均、流体速度分布不均、湍流强度不均等不足,有利于污染物的传质和分解。计算流体力学(CFD)可有效模拟反应器内部流场、粒子图像测速技术(PIV)可直观观测反应器内部流场,结合这两种技术可为反应器的性能研究和结构优化提供可靠的依据。本文采用CFD与PIV相结合的方式,分别模拟和测试了不同进口方式(轴向、径向和切向)对反应器的影响,分析了反应器进口区域的速度场和整个反应器的压强降等水力特性。结果显示,模拟结果与测试结果基本一致,进口区域属流体流动的过渡区域,受进口方式的影响较大。相比其他两种进口方式,切向进口的速度分布均匀,没有大的速度梯度,没有回流死区,电极表面流速也比较适合,且压降最小。其次,通过DPM模型,分析了不同气泡直径和质量流量对反应器内部流场的影响。模拟结果表明,气泡对连续相流场的影响随着气泡直径的增大而增大,气泡直径较小时,气泡增强湍动且使流场分布变得均匀,而直径较大时,反应器上下部分湍动强度分布不均匀,上端湍动剧烈,而下端出现低湍动区;当气泡量少时,连续相流动起主导作用,气泡对湍动强度的影响不明显,随着气泡的增多,气泡效应越来越明显,流场分布变得越来越均匀。最后,分别从流场分布和传质性能两方面对比分析了MPE-PFER和PFER的性能。从流场来看,MPE-PFER中流场受进口区域影响小,流场可以更早达到稳定,稳定后径向流速分布更加均匀,在网孔处达到速度峰值;PFER中电极间流场呈抛物线型分布,流场受进口区域影响较大。通过对两种反应器传质半经验公式的分析发现,由于网板电极的存在,MPE-PFER的传质性能明显高于PFER,MPE-PFER的传质关联式是PFER的23.061.4?u倍,在相同的流量变化下,MPE-PFER传质系数提高的是PFER的两倍。更多还原

【Abstract】 The plug flow electrochemical reactor(PFER) is a novel electrochemical treatment technology which can improve the current efficiency and reduce the processing costs. The plug flow electrochemical reactor with mesh plate electrode(MPE-PFER) solved the weakness of traditional plug flow electrochemical reactor and improved the mass transport of pollutant, such as uneven current density distribution, disunion fluid velocity distribution and non-uniform turbulence intensity, due to the same electrodes size and the fluid flows through the electrode surface perpendicularly. Computational Fluid Dynamics(CFD) can effectively simulate the flow field inside the reactor, Particle Image Velocimetry(PIV) can directly show the flow field in a reactor, the combination of these two techniques can provide a reliable basis for the optimization of reactor performance and structure.In this paper, the combination of Computational Fluid Dynamics(CFD) and Particle Image Velocimetry(PIV) were used to simulate and test the flow field and pressure drop with different inlet(axial, radial and tangent). The results show that the simulation results and test results are basically the same. As a transitional area of fluid flow, the inlet region impact by inlet way greatly. Compared to the other ways of inlet, for tangential inlet, velocity distribution is uniform, no large velocity gradients, no reflux dead zone, the flow rate of the electrode surface is also more suitable, and the pressure drop is least.Secondly, by DPM model, the effects of different bubble diameter and mass flow rate to flow field inside the reactor were analyzed. The simulation results show that the impact of bubbles on the continuous phase flow field increases as the bubble diameter increases. When the bubble diameter is small, it can enhance the turbulence and uniform the flow field distribution, the diameter is larger, the turbulence intensity distribution of reactor upper and lower part is uneven, the upper part turbulent intensively, while the lower part appear the low turbulent region. When the bubble mass flow rate is less, the flow of continuous phase plays a dominant role, the impact of bubbles on the turbulent intensity is not obvious, with the increase of the bubble, bubble effect more obvious, the flow field distribution becomes more uniform.Finally, the flow field distribution and mass transfer performance of both MPE-PFER and PFER were comparative analysed. From the view of flow field, the effect by inlet region of MPE-PFER flow field is small, the flow field can be stabilized earlier, velocity distribution in the radial direction and velocity peaks were obtained to the electrode holds, the flow field distribution between the electrodes in PFER was parabolic, the flow field influenced by the inlet area is small. By analyzing the mass transfer semi-empirical formula for both reactors, we found that the mass transfer performance of MPE-PFER is higher than PFER significantly due to the presence of mesh plate electrode, the mass transfer correlation of MPE-PFER is 23.061.4 ?u times as much as PFER, under the same flow change, the increased mass transfer coefficient of MPE-PFER is twice as large as PFER.更多还原