Model Analysis of Mixing Time Correlation in an Agitated Vessel with Paddle Impeller

From a new model obtained by combining the circulation model with the eddy diffusion model two dimensionless parameters were derived to correlate the mixing time with the power number and the discharge flow rate number for an agitated vessel with paddle impeller. The parameter which contained the mixing time was Y = (ntM)(Nqd)(d/D)3(D/H) and the one which contained the pumping efficiency number was X = {(D/d)4Np/Nqd3}1/4(H/D)1/2. These parameters Y and X were used to correlate the mixing time measured by several researchers, who measured the mixing time, the power number and the discharge flow rate number at the same time. The mixing time correlation obtained was expressed by Y = 6.7X-1, which was rewritten by the following expression. ntM = 6.7(D/d)2(Np·Nqd)-1/4(H/D)1/2    The mixing time estimated from the correlation well agreed with those from the empirical correlations reported before within the experimental error. The simulated result of the mixing time for a pitched blade paddle impeller by Patwardhan and Joshi (1999) was also correlated well with the obtained mixing time correlation.