Dynamics of flow macro-formation and its interference with liquid surface in mixing vessel with pitched blade impeller

► In this study we examine flow pattern in axially stirred vessel with PBT. ► We investigated behaviour of flow macro-formations generated by primary circulation loop. ► Our developed theoretical model is compared with experimentally obtained data. ► Regarding to introduced simplifying assumption we confirm correctness of theoretical model. The paper deals with the experimental and theoretical study of flow pattern dynamics and their manifestation on the liquid surface in a flat bottomed cylindrical stirred vessel with inner diameter T = 0.29 m, filled with water to the height H = T. The vessel was stirred by down pumping a six-pitched blade impeller with pitch angle 45°, pumping downwards. Based on flow visualization in a vertical, and three horizontal planes, parameters describing flow macro-formation behaviour during its generation by the primary circulation loop, including the total time of flow macro-formation existence, were obtained. These experimental results were compared with the results calculated from a proposed theoretical model of flow macro-formation dynamics. In the next part of the contribution, the theoretical solution of quantitative expression for liquid surface swell dimensions is presented. The liquid swell is supposed to be an effect resulting from an interaction between the surface level and the flow macro-formation. The data obtained from the theoretical solution are compared with swell dimensions determined from the visual analysis of the liquid surface behaviour. Finally, the comparison of experimental and theoretical results is statistically analyzed and corresponding summaries are concluded.