The Identification of Leidenfrost Phenomenon Formation on TiO2-Coated Surfaces and the Modelling of Heat Transfer Processes

Abstract

Experiments on specimen cooling dynamics and possible film boiling around a body are very important in various industrial applications, such as nucleate boiling, to decrease drag reduction or achieve better surface properties in coating technologies. The objective of this study was to investigate the interaction between the heat transfer processes and cooling dynamics of a sample in different boundary conditions. This article presents new experimental data on specimens coated with Al–TiO2 film and Leidenfrost phenomenon (LP) formation on the film’s surface. Furthermore, this manuscript presents numerical heat and mass transfer parameter results. The comparative analysis of new experiments on Al–TiO2 film specimens and other coatings such as polished aluminium, Al–MgO, Al–MgH2 and Al–TiH2 provides further detail on oxide and hydride materials. In the experimental cooling dynamics experiments, specimens were heated up to 450 °C, while the sub-cooling water temperatures were 14*‒20 °C (room temperature), 40 °C and 60 °C. The specimens’ cooling dynamics were calculated by applying Newton’s cooling law, and heat transfer was estimated by calculating the heat flux q transferred from the specimens’ surface and the Bi parameter. The metadata results from the performed experiments were used to numerically model the cooling dynamics curves for different material specimens. Approximated polynomial equations are proposed for the polished aluminium, Al–TiO2, Al–MgO, Al–MgH2 and Al–TiH2 materials. The provided comparative analysis makes it possible to see the differences between oxides and hydrides and to choose materials for practical application in the industrial sector. The presented results could also be used in software packages to model heat transfer processes.