The volumetric mass transfer coefficient k(L)a becomes the crucial parameter for mechanically agitated fermenters design. Prediction of k(L)a is commonly based on literature correlations. In the case of coalescent liquids, literature-based correlations don't provide results with acceptable scatter. Our aim is to establish viable k(L)a correlations for coalescent liquids that would be based on great experimental data set obtained using Dynamic Pressure Method, the physical correctness of which was verified earlier. In our previous work, the k(L)a dependencies on process conditions in a viscous liquid were described in terms of an appropriate correlation. Now, we aim at the description of dependency between impeller diameters and transport characteristics in coalescent batch. The measurements were performed in multiple-impeller vessels of both laboratory and pilot-plant scale, and for various experimental conditions (impeller frequencies, gas flow-rates, impeller diameters). The studied impellers were Rushton turbines with diverse diameters. On the base of experimental results, the accurate correlation for k(L)a prediction in coalescent batch for industrial devices was suggested. Both the experimental technique and the correlation shape could be used for an industrial design of fermenters with coalescent batches. (C) 2018 Elsevier Ltd. All rights reserved.