Session: K8-03: FUNDAMENTALS OF MULTI-PHYSICS TRANSPORT AND MACHINE LEARNING

Paper Number: 137910

137910 - Understanding Water Evaporation Under Visible Light Illumination 

Abstract: 

Solar driven evaporation of water is a ubiquitous phenomenon powering the global water cycle as well as numerous industrial applications.  However, water is almost completely transparent in the visible spectrum, which is 44% of the solar irradiance on the surface of the earth, and water is strongly absorbing in the infrared wavelength range. This has prompted the utilization of photothermal converters to enable the efficient utilization of solar energy for evaporation via heat localization.  Different experimental results suggest that the evaporation rate can exceed the thermal limit of evaporation, which is typically calculated with the relationship of the applied energy to the vaporization enthalpy. Beating this limit means a miscalculation of the available environmental energy or vaporization enthalpy through unaccounted for phenomena.  One set of recently published experimental results show evaporation rates exceeding the thermal limit under visible light illumination. These experiments also suggest that water may be more absorbing at visible wavelengths than current theories suggest for specific polarization and incident angle conditions. Previous literature has theorized that these unique properties may be due to water clusters. Water clusters have been theorized to explain the anomalous properties of water since Röntgen in the 19th century. Liquid water, traditionally characterized with a complex hydrogen bond network, is typically contrasted with a gaseous phase of disassociated water molecules. However, the continuity of phases established by the triple point implies an intermediate state between the liquid and gas phase.  This intermediate state of water clusters may explain the unexpected optical and thermodynamic properties of water; various water cluster configurations have been predicted with Ab Initio techniques over the last 20 years. The current study investigates the enhanced optical absorption of water and its corresponding effect on evaporation rates.  Further exploration and physical insight into the effects of the visible light on evaporation can contribute to improved vapor generation technologies while simultaneously elucidating information about earth’s water cycle. 

Presenting Author: Preston Bohm Georgia Institute of Technology

Presenting Author Biography: Preston Bohm is a Ph. D. student at Georgia Institute of Technology.

Authors:

Preston Bohm Georgia Institute of Technology
Fangzhou Wang Georgia Institute of Technology
Akanksha K. Menon Georgia Institute of Technology
Zhuomin M. Zhang Georgia Institute of Technology