Single and multiple drop impact onto heated surfaces

The study of drop impact onto solid heated surfaces is important in many industrial applications, such as the metal surface cooling in the steel industry and in the nuclear power plants, the hot coating treatment of surfaces, the diesel and gasoline direct injection, the thermal control of electronic devices. The number of boundary conditions and parameters is enormous and it is still missing a systematic description of the process in the different thermal and fluid-mechanical conditions in which it can happen. The drop impact process onto heated surfaces has different regimes. The boiling start-up during the drop spreading radically changes the impact dynamics. The secondary atomization is not generated through the so called “crown splash”, but by the vapour bubble explosion at the liquid interface of the spreading lamella. The present paper will resume some of the results obtained in the last years by the research group of Thermodynamics and Heat Transfer at the Industrial Engineering Department in Bergamo.