Evaporation of Leidenfrost droplets on microtextured substrates

Prasad, D and Dash, S (2024) Evaporation of Leidenfrost droplets on microtextured substrates. In: International Journal of Thermal Sciences, 197 .

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Abstract

A thin thermally insulating vapor layer beneath a levitating Leidenfrost droplet adversely affects the heat transfer from the underlying hot substrate during cooling applications. In this work, we present a theoretical model to determine the total heat transfer to a Leidenfrost droplet on microtextured substrates, taking into account the curved shape of the liquid-vapor interface. The profile of the vapor gap and vapor flow field beneath a Leidenfrost droplet on a microtextured surface is shown to be dependent on the substrate morphology. The shape of the liquid-vapor interface beneath the Leidenfrost droplet, in turn, influences the rate of evaporation on a microtextured substrate. We determine the variation of the minimum and maximum vapor gap over micro-pillared surfaces with different substrate permeability for various droplet volumes and wall superheat. The heat transferred to the droplet is via conduction across the vapor gap beneath the droplet and convection from the ambient air around the droplet. We determine the total evaporation time of a Leidenfrost droplet over a micro-textured substrate using the curved interface model and the conventional flat vapor gap interface model and compare with that obtained from experiments. The overprediction of the average rate of evaporation of a Leidenfrost droplet by the flat interface model ranges from ∼59 % for tall and sparse pillars (marked by high substrate permeability) to ∼ 29 % for short pillars (with low substrate permeability). We show that the average rate of evaporation of the LF droplet obtained using the curved interface model agrees reasonably (within 9%–23 %) with that observed in the experiments. © 2023 Elsevier Masson SAS

Item Type:	Journal Article
Publication:	International Journal of Thermal Sciences
Publisher:	Elsevier Masson s.r.l.
Additional Information:	The copyright for this article belongs to Elsevier Mosson SAS.
Keywords:	Drops; Evaporation; Heat transfer; Morphology; Textures, Curved interface; Curved interface model; Evaporation time; Interface modeling; Leidenfrost droplet; Liquid-vapor interface; Microtextured substrates; Substrate morphologies; Substrate permeability; Vapor gap, Substrates
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	19 Jan 2024 10:39
Last Modified:	19 Jan 2024 10:39
URI:	https://eprints.iisc.ac.in/id/eprint/83603

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