The hydrodynamics of a liquid droplet impinging on a particle is of direct relevance to many engineering applications. The mechanism of heat and mass transfer during the droplet solid collision is essential to the design and operation of many industrial systems. However, very limited systemic research is available to describe the droplet impact on hot solid spheres.

This paper aims to establish a systematic investigation of phase transfer due to the droplet-solid impact, by both experimental and modeling approaches. The targeted phase transfer includes the surface attachment, mass of vaporization, heat transfer to droplet and its partition between vaporization and droplet heat-up. Specific experiments were designed and performed to partially validate the model predictions on the droplet-solid phase transfer. A simple mechanistic model is proposed for the parametric study of droplet and solid sphere collision. Effects of the droplet size, velocity and the off-centre condition on the outcome of the collision are analyzed. In addition, the geometric effect, bridge effect of two and three balls and the effect of collision on heat transfer among droplet and solid sphere are also illustrated. The theoretical results agree reasonably with the experimental measurements.