Triple condensate halo from water droplets impacting on cold surfaces

TL;DR

This study reveals the formation of a triple condensate halo during water droplet impact on cold surfaces, combining experimental observations with a scaling model to understand the underlying heat and mass transfer processes.

Contribution

It introduces the first detailed analysis of the triple condensate halo phenomenon and develops a validated scaling model for its size based on impact dynamics and vapor diffusion.

Findings

Identification of three distinct condensation bands during droplet impact

Development and validation of a scaling model for halo size

Insights into heat and mass transfer during droplet impact on cold surfaces

Abstract

Understanding the dynamics in the deposition of water droplets onto solid surfaces is of importance from both fundamental and practical viewpoints. While the deposition of a water droplet onto a heated surface is extensively studied, the characteristics of depositing a droplet onto a cold surface and the phenomena leading to such behavior remain elusive. Here we report the formation of a triple condensate halo observed during the deposition of a water droplet onto a cold surface, due to the interplay between droplet impact dynamics and vapor diffusion. Two subsequent condensation stages occur during the droplet spreading and cooling processes, engendering this unique condensate halo with three distinctive bands. We further proposed a scaling model to interpret the size of each band, and the model is validated by the experiments of droplets with different impact velocity and varying substrate temperature. Our experimental and theoretical investigation of the droplet impact dynamics and the associated condensation unravels the mass and heat transfer among droplet, vapor and substrate, offer a new sight for designing of heat exchange devices.