The maximum entropy principle (MEP) is one of the firstmethods which have been used to predict droplet size and velocity distributions of liquid sprays. Thismethod needs amean droplets diameter as an input to predict the droplet size distribution. This paper presents a newsub-model based on the deterministic aspects of liquid atomization process independent of the experimental data to provide the mean droplets diameter for using in the maximum entropy formulation (MEF). For this purpose

a theoretical model based on the approach of energy conservation law entitled energy-based model (EBM) is presented. Based on this approach

atomization occurs due to the kinetic energy loss. Prediction of the combinedmodel (MEF/EBM) is in good agreement with the available experimental data. The energy-basedmodel can be used as a fast and reliable enoughmodel to obtain a good estimation of the mean droplets diameter of a spray and the combined model (MEF/EBM) can be used to well predict the droplet size distribution at the primary breakup.