Power characteristics for an agitated vessel equipped with planar short baffles of length L and pitched blade turbine of pitch β are presented in the paper. The studies were carried out in the vessel of inner diameter D = 0.6 m, where the baffles were located in the distance p from the vessel bottom (p + L = H). Torque was measured using strain gauge method within the turbulent regime of the flow of Newtonian liquid in the agitated vessel. The effects of the pitch β and geometrical parameter p/H on the power number Ne were determined mathematically. The results showed that, for the assumed value of the angle β, the function Ne = f (L/H) decreases with the decrease in the baffle length L (i.e. with the increase in the parameter p). Moreover, for the assumed value of the baffle length L, the function Ne = f (β) increases with the increase in the angle β of the inclination of the impeller blade.

The results of the power consumption for an agitated vessel equipped with vertical tubular baffles and high-speed impeller are presented in the paper. Aqueous solutions of CMC were agitated within transitional range of the non-Newtonian liquid flow in the agitated vessel of inner diameter equal to 0.6 m. Eight different types of the impellers were tested: Rushton or Smith turbines, turbine with straight blades, pitched blade turbines and propeller. The J tubular baffles of outer diameter B were located in the position e from the vessel wall. Different configurations of baffles, arranged around the vessel circumference singularly or blocked in the modules, were considered in the study. In total, 180 different tubular baffles–impeller systems were tested. The measurements of the torque were conducted by means of the strain gauges method. Based on the power characteristics obtained for each impeller type, the effect of the geometrical parameters of the vertical tubular baffles on the power number was determined and discussed. The results show that geometry of the tubular baffles mostly affects the power number for the system with radial flow Rushton turbine. Moreover, power numbers decrease with the increase of the clearance between baffle and vessel wall for the systems, in which the radially axial circulation of the liquid is promoted. The dependences of the power number on the geometrical parameters of the vertical tubular baffles arranged singularly around the vessel circumference were described by means of the Eqs. (5)–(16). These equations can be useful in the project computations.

Results of the experimental research on gas hold-up, power consumption for liquid phase and gas—liquid systems, and on residence time of the gas bubbles are presented in the paper for an agitated vessel with a turbine impeller. Distilled water or aqueous solutions of NaCl were used as the liquid phase. Air was dispersed into liquid as the gas phase. The studies were carried out in an agitated vessel of the inner diameter D = 0.634 m. Tubular baffles of the diameter of 0.7D, consisting of 24 vertical tubes of the diameter of 0.016D, were located inside a flat-bottomed tank. Turbines with six blades and the pitch of 90°, 60°, or 45°, respectively, were used for agitation. Measurements were carried out in the range of good dispersion of gas bubbles in the liquid within the turbulent regime of the liquid flow. Effects of the gas bubbles capability to coalesce on the gas hold-up, residence time of the gas bubbles, and power consumption were analyzed. Results of the power consumption (P G-L/P o = f 1(Kg, Fr)) and gas hold-up (φ= f 2(Kg, We, Y)) were approximated mathematically, using Eqs. (5) and (6), respectively. In Eq. (6), parameter Y was introduced in order to describe the influence of the bubbles capability to coalesce on the gas hold-up. The results of the study show that power consumption does not depend on the capability of bubbles to coalesce, but the pitch of the turbine impeller affects the power characteristics in such a physical system significantly. However, the residence time of the gas phase in agitated liquid depends on the pitch of the impeller blade and on the capability of bubbles to coalesce.

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A comparative analysis concerning the influence of different factors on momentum transfer in mechanically agitated systems was carried out on the basis of experimental results for solid-liquid, gas-liquid and gas-solid-liquid systems. The effects of the impeller -baffles system geometry, scale of the agitated vessel, type and number of impellers and their off-bottom clearance, as well as physical properties of the multiphase systems on the critical impeller speeds needed to produce suspension or dispersion, power consumption and gas hold-up were analysed and evaluated.