Heat transfer coefficients and two‐phase dispersion properties in a stirred‐tank fermentor

Abstract

Abstract Experiments were performed in a pilot scale 0.30 m 3 conventional stirred‐tank fermentor using water, air/water, and air/K 2 SO 4 solutions. Both single‐ and two‐stage impeller systems were investigated. Overall and tank‐side coefficients for heat transfer from a 0.012 m diameter coil were measured for a range of impeller speeds and superficial gas velocities. Power input, bubble size, and gas hold‐up were also determined. An analysis of the experimental results indicates that previously published correlations for single‐phase heat transfer in stirred tanks (of the type: Nu = C (Re) α (Pr) β ) are not applicable for single‐ or multiimpeller gas/liquid systems. The introduction of air alters the mixing pattern significantly, affecting both average and local tank‐side heat transfer coefficients. Power input and gas hold‐up are suggested as the major correlating parameters for the determination of tank‐side heat transfer coefficients.