Film boiling of mercury droplets

Abstract

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting: therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed‐form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

Leidenfrost drop dynamics: a forgotten past and modern day rediscoveries

“…By the 1960s when work on the Leidenfrost effect was starting to experience a resurgence in interest, the American engineers Glen J Schoessow and Kenneth J Baumeister, on stumbling across star-shaped patterns formed in Leidenfrost drops likewise believed it to be a new discovery [27]. It was only some years later in 1977 [28] when the pair conceded their work of eleven years earlier was a rediscovery of the work of Holter and Glasscock, which in turn though going unrecognised, was a rediscovery of much earlier work stemming all the way back to Laurent.…”

“…Since the time of Holter and Glasscock the formation and behaviour of star-shaped patterns in Leidenfrost drops has been extensively studied [27,28, and is still an object of interest today [156][157][158][159][160][161][162][163][164][165][166][167][168]. According to Ma et al [160] and Ma and Burton [162] the vibrations seen in Leidenfrost drops are thought to be initiated and driven by a parametric forcing mechanism arising from pressure variations in the vapour layer.…”

“…were once sessile can suddenly and quite unexpected start to oscillate in a radial direction to form either elliptical patterns with two lobes or more general hypotrochoid patterns with three or more lobes [25][26][27][28]. More recently, other equally intriguing dynamical behaviour in Leidenfrost drops have been observed.…”

Film evaporation of drops of different shape above a horizontal plate

“…A great many experimentally based papers focus on the influence of ambient pressure [3,4], the type of liquid [5][6][7] and surface parameters (roughness, temperature and material) [4,8,9] on the evaporation time of large single drops. In addition, mathematical models were developed by Gottfried et al [2], Wachters et al [10] and Baumeister et al [11], thus facilitating the calculation of the vapor film thickness and the rate of evaporation.…”