The effects of curvature, pitch, tube length, flow rate and GT value (the product of root-mean-square velocity gradient and detention time) of a helical secondary-flow mixer used in coagulation with polyaluminum chloride (PAC1) on its performance were investigated. The helical secondary-flow mixer was prepared by twining a rubber tube round a cylinder, and kaolin suspension was used as simulated wastewater for this experiment. It was found that tube length, curvature and flow rate of the mixer had highly significant impacts on mixing effect, similarly pitch had significant impact. And the impacts of the four factors decreased as follows: tube length, flow rate, curvature and pitch. 12 m was the optimal tube length among three tube lengths of 12 m, 18 m and 24 m. As for electrically neutral coagulation, the secondary-flow mixer with a tube length of 24 m also achieved an excellent mixing effect. In addition, there existed two optimal GT values for both electrically neutral and sweep coagulation. Theoptimal GT values were 21000 and 35000 for the former, and 19000 and 32000 for the latter.%考察了以聚合氯化铝(PACl)作为混凝剂时,混合器的曲率、螺距、管长、水流速率以及混合过程的GT值等对螺旋管式二次流混合器混合性能的影响.研究发现,混合器的管长、水流速率以及曲率对该混合器混合性能具有高度显著影响,而螺距具有显著影响,四者影响的显著性由高到低依次为管长、水流速率、曲率和螺距；实验范围内,二次流管的最佳长度为12 m,且在电中和及卷扫混凝时均出现两个最佳GT值.
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