This work concerns the modeling of the dynamics of a vapour-droplets flow. The context is the study, using numerical simulations at a CFD scale, of the heat transfer downstream the quench front during the reflood step of loss of coolant accident in the core of the reactor of a nuclear power plant. The analysis of the physical phenomena that govern the spatial distribution of the droplets over the flow has been performed. The weakness of some modelings concerning (i) the lift force and (ii) the turbulent dispersion of the droplets has led to the development of some new formulations of the models. The consequences of these improvements on the wall to fluid heat transfer in the context of study has been analized.