Leidenfrost evaporation of water droplet

Abstract

The present paper examines the behaviour of a single large droplet levitating over a hot surface, unsteady mass of the droplet, and heat transfer. It was assumed that the evaporation from the upper surface of the droplet is negligibly small compared with the amount discharged from its lower surface, and the heat transfer coefficient is the power function of droplet orthogonal projection onto the heating surface. Based on the photographic documentation, the dependence of the droplet projection on time was approximated. A heat balance was written in the form of a non-linear first order differential equation. The solution to the equation was included. The analytical function of droplet mass change in time was used to determine the exponent of the power dependence of the heat transfer coefficient on the orthogonal droplet projection onto the heating surface. The comparison showed the method proposed in the study could be applied to analyse the behaviour of a water drop levitating above a surface at the temperature higher than the Leidenfrost point.

Peculiarities in Leidenfrost water droplet evaporation

“…In the paper conclusions, the authors postulated linear dependence between droplet lifetime and its initial volume and inversely proportional relation between droplet lifetime and temperature. In the study [24], it was shown that in order to apply this dependence for different parameters, is it necessary to choose the base of power on case-by-case basis. That additionally makes it difficult to apply the formula for general use.…”

“…The droplet projection formula does not depend on the initial droplet mass, which was confirmed by reported measurements. The proposed dependence was used by Orzechowski [24], who worked out a formula, expressed as infinite series, for droplet mass change over time. The effective application of the formula, however, makes it necessary to individually select coefficients that describe the area of the droplet projection.…”