The critical temperature of dry impact for tiny droplet impinging on a heated surface

Leidenfrost temperature has long been taken as the criterion to classify characteristic regimes for not only heat transfer but also hydrodynamic impact patterns for droplet impinging on a heated surface. This work classifies the characteristic impact regimes and reveals that the hydrodynamic impact parameter influences the classification of characteristic impact regimes. For each individual impact, the required surface temperature for the dry impact, which has no direct liquid–solid-contact during the impact period is much lower than the Leidenfrost temperature. The squeeze film effect has been successfully used to explain the corresponding mechanism for it.