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Preferential concentration and clustering influences the heat and mass transfer for spray droplets.The effect of droplet clustering is of interest for many spray applications,e.g.in automotive spray combustion.In this paper the meso-scale droplet clustering in sprays is investigated.Droplet clustering here is mainly caused by the droplet interaction with eddy structures in the gas flow.In order to simulate the vortex formations in the gas flow the Large-Eddy-Simulation(LES)approach has been used.The heat transfer between the droplets and the gas is analysed with respect to local concentration inhomogeneities.The results of this study indicate that the effect of the spatial inhomogeneity of the droplet concentration on the heat transfer in cluster is of importance in areas of local Stokes regimes slightly larger than unity.The resulting cluster structures on the spray axis are long-living and their formation process is a non-spontaneous.The results of the numerical simulation are compared with Particle-Image-Velocimetry measurements.The spray morphology,namely the droplet clusters,as well as statistical values of the flow variables for the dispersed phase agree well in experiment and simulation.