Vortex Depth Analysis in an Unbaffled Stirred Tank With Concave Blade Impeller

Abstract

Abstract. 1 The present study was carried out by experimenting in a stirred tank of unbaffled system employed with concave blade impeller. In this study the influence of impeller diameter (d), tank diameter (D) and impeller clearance depth ( C ) on vortex depth is investigated at various impeller rotational speeds. The higher vortex depth is observed when the impeller is closer to the tank bottom. Relative vortex depth increases with the increase in the impeller diameter in all cases of impeller clearance depth at constant D. Smaller tank diameter gives higher relative vortex depth, when d is constant at different impeller clearance depths. Critical speed is found decreasing with the increase in C/D and d/D ratio. Finally, a scale up criteria for relative vortex depth has been developed, which is valid for geometrically similar conditions.

Batch reactor scale-up of the mixing-sensitive Bechamp reaction based on the heat pulse method

“…The vortex depth is visually determined but can also be calculated using the equations summarised by Markopoulos & Kontogeorgaki (Markopoulos & Kontogeorgaki, 1995). These equations use a vortex factor (hv/hv,max), which is the ratio of the vortex depth (hv) to the maximal vortex depth (hv,max), where the vortex reaches the stirrer blades (Devi & Kumar, 2017;Dickey, 2015;Markopoulos & Kontogeorgaki, 1995;Myers et al, 2002).…”

Vortex Formation and Subsequent Air Entrainment inside a Liquid Pool

“…Researchers − have also employed the volume of fluid approach based numerical techniques to study the gas entrainment inside reactor vessels. It can be observed that the genesis of air entrainment is mainly studied as outflow induced vortex in the liquid pool; however, researchers have also investigated entrainment patterns, either in the form of vortex in unbaffled stirred tanks − or as discontinuous entrainment of air entities in baffled stirred vessels. − Moreover, it is to be mentioned that all these efforts − have utilized the impellers or mechanical agitators to impart the rotational field to the fluid medium and, at the same time, the shaft of the prime mover holding impeller has interfered with the entrained vortex core. Such mechanical agitator induced swirling motion has led to the occurrences of various biasing features including excessive stress of shaft, loss of mixing power, imbibition of gases into liquid, vibrations, noise, and genesis of large amplitude circumferential waves .…”

“…Therefore, the estimation of vortex tip penetration has remained the topic of prime interest for the chemical and process industry. Researchers − over the last few decades have found the impeller diameter based Froude number as the controlling parameter for vortex penetration. Further, Rieger et al have used the Galileo number to consider the effect of liquid velocity and impeller size variation.…”