Experimental and numerical studies on mass transfer characteristics behind an orifice in a circular pipe for application to pipe-wall thinning
Experimental and numerical studies on mass transfer characteristics behind an orifice in a circular pipe for application to pipe-wall thinning
复制标题
DOI：
10.1016/j.expthermflusci.2013.09.017
复制
发表时间：
2014
影响因子：
3.2
通讯作者：
T. Yamagata;Akihiro Ito;Yuki Sato;N. Fujisawa
中科院分区：
文献类型：
--
作者：
T. Yamagata;Akihiro Ito;Yuki Sato;N. Fujisawa
针对核电站/化石厂管道中由于流动加速腐蚀而导致管壁减薄的问题，通过实验和数值模拟研究了孔口后圆管内的传质特性。采用苯甲酸在水流中溶解的方法进行传质系数的测量，可以在接近管道实际运行条件的施密特数下测量圆管孔板后的传质。孔后传质系数的测定表明，由于湍流的影响，在孔后1-2个管径的区域内，舍伍德数最大，向下游逐渐减小，这与文献中管壁减薄的特征定性一致。结果表明，随着施密特数和雷诺数的增加，孔后的舍伍德数显著增加，但孔后流的变薄率与充分发展管流的变薄率之比的几何因子对这些参数的依赖性较弱。数值模拟结果表明，采用k-ε模型对高Schmidt数流动进行经验修正后，数值模拟结果较好地再现了实验得到的舍伍德数分布和孔口后的平均速度分布，但对最大舍伍德数的预测略有偏高，反映出对孔口后湍流能量的预测偏高。这些结果表明，数值模拟对于预测由于流量加速孔流中的腐蚀而导致的管壁变薄是有用的。
Experimental and numerical studies are carried out to understand the mass transfer characteristics in a circular pipe behind an orifice, which is often encountered in pipe-wall thinning due to flow accelerated corrosion in pipelines of nuclear/fossil power plants. The measurement of mass transfer coefficient is conducted by using benzoic acid dissolution method in a water flow, which allows the measurement of mass transfer behind the orifice in a circular pipe at the Schmidt number near the actual operating condition of the pipeline. The measurement of mass transfer coefficient behind the orifice shows a maximum Sherwood number in the region 1–2 pipe diameters downstream of the orifice due to the flow turbulence, and it decreases gradually in the downstream, which agrees qualitatively with the feature of pipe-wall thinning in the pipeline in literature. The present result indicates that the Sherwood number behind the orifice is greatly increased by increasing the Schmidt number and the Reynolds number, though the geometrical factor, which is the ratio of the thinning rate of the orifice flow with respect to that of the fully developed pipe flow, is weakly dependent of these parameters. It is also found that the experimental Sherwood number profiles and the mean velocity distribution behind the orifice are well reproduced in the numerical simulation by thek–εmodel with the empirical modification of high-Schmidt-number flows, though the maximum Sherwood number is slightly overpredicted, reflecting the higher prediction of turbulence energy behind the orifice. These results demonstrate the usefulness of the numerical simulation for predicting the pipe-wall thinning due to the flow accelerated corrosion in the orifice flow.