Flow Patterns of Liquids in a Cylindrical Mixing Vessel with Baffles

Abstract

The velocity distribution of a liquid in a cylindrical mixing vessel with flatplate-baffles was measured by a method similar to that adopted in the case without baffles. Some of the experimental results are shown in Figs. 3, 4, 5, 6, 7, 8 and 9. Variations of the liquid velocity distribution caused by inserting baffle-plates are shown in Fig. 10. Obviously, the insertion of baffle-plates reduces the circulation flow around the impeller axis (the tangential component vₜ of liquid velocity) and increases the circulation flow in the vertical direction. The discharging performance of various impellers is represented by the ratio NₚB/Nq₁, which is the dimensionless factor corresponding to the relative power required for the unit quantity of discharge. The comparisons of these ratios for various impellers are shown in Table 3, together with those for the non-baffled condition. It is to be noted that, in spite of a considerable increase in Nq₁ the circulation efficiency of the agitators is eventually lowered by inserting baffle-plates. Furthermore, the power consumption in the neighbourhood of the impeller (Nᴘᵢₚₘ) was calculated and compared with that consumed in the outer region of the vessel (ΔNₚ) as shown in Table 4, It may be considered that the improvement in the circulating capacity is accomplished by the proper design of the baffle-plates.