The generalised coalescence/redispersion (gCR) micromix ng model is formulated in the framework of the three scale mixing concept of stirred tank reactors. It is developed on the basis of a random coefficient differential equation system describing mass exchange interactions between the Kolmogorov scale fluid elements the average behaviour of which is modelled using the population balance approach. The model provides closed terms for both the chemical reactions and micromixing and it allows computing processes with either pro mixed or unmixed feeds of reactors. A qualitative picture of producing the fluid elements in the eddy space as Kolmogoro microscale eddies, interpreted as mesomixing of the three scale mixing model is outlined. The population balance equation is reduced to a moment equation system for joint moments of concentrations using the standard moment method which is closed by cumulant-neglect closure. The gCR model is validated by fitting the model to literature data of bimolecular quasi-linear chemical reactions (Miyawaki et al., 1975. J. Chem. Eng. Jpn. 8,63-68, Takao et al., 1978. J. Chem. Eng. Jpn. 11,481-486), and of a quasi-linear consecutive-competitive chemical reaction system (Paul and Treybal, 1971, AlChE J. 17, 718-724) in stirred tank reactors. It is pointed out by simulation that in case of non-homogeneous micromixing space of stirred tank reactor different inlets-outlet configurations of mixing experiments produce significantly different concentration responses, and using the gCR model micromixing inhomogeneities can be explored. (C) 2014 Elsevier Ltd. All rights reserved.