Investigation of Torque and Horizontal Load on a Paddle Impeller in Eccentric Mixing

Abstract

The present study investigates the torque and horizontal load in eccentric mixing by measurement under various operating conditions. Time series data of torque and horizontal load were obtained, showing that torque and the horizontal load were periodically oscillating. Time-averaged torque in the laminar region and in the turbulence region increased proportionally with n and n², respectively. A power number Np [—] vs. Reynolds number Re [—] diagram was obtained. For various mixing liquids, Np-Re correlated with one curve. For Re<10, Np was independent of r_E. However, in the higher Re region, Np was proportional to r_E. The torque in eccentric mixing was estimated from this figure. The time-averaged horizontal load, F_avg, also increased with n. In the lower Re region, F_avg was proportional to n. However, for Re>10⁴, F_avg was proportional to the square of n. A dimensionless number related to the horizontal load, Np_Favg [—], was defined as Np_Favg=n F_avg d/ρ n³ d⁵. An Np_Favg-Re diagram almost correlated with one curve at each r_E and Np_Favg was proportional to r_E irrespective of Re. The horizontal load in eccentric mixing was estimated from this figure.