水中胶体微粒在管道中的对流传质分析

Convective mass transfer of colloidal particles in water in vertical tubes

对常物性条件下，水中含有的金属腐蚀产物微小颗粒在管道中的层流与紊流对流传质，在壁面上杂质的质量分数或质流密度为常数的条件下进行了理论分析和数值计算，给出了对流传质问题的理论解及计算关联式。结果表明：Ｌｅ越大，扩散边界层越薄。质量分数的剧烈变化发生在紧靠壁面的一薄层内。对于紊流对流传质，当离管壁的量纲为一的距离小于６时的质量分数分布对传质的影响甚大，因此，对紊流传质必须采用修正的紊流模型，而不能简单地假设紊流施密特数等于１。

Laminar or turbulent forced convective mass transfer in vertical tubes is analyzed theoretically and studied numerically for water containing micro particles of metallic corrosion products under constant concentration or mass flux boundary conditions with constant thermophysical properties. Theoretical solutions and several mass transfer correlations are presented. It is found that the diffusive boundary layer becomes thinner with increasing Le number and a sharp variation of the concentration occurs in a very thin layer near the wall ( η< 6). Therefore, since the concentration distribution at η <6 greatly influences the convective mass transfer, a modified turbulent mass transfer model must be used rather than simply assuming that Sc T=1.