Transpiration through hydrogels

We present experiments and theory relating to transpiration through unrestrained hydrogel beads in contact with a water reservoir below and air above. Experimentally, we find that saturated hydrogel beads shrink until a steady state is reached in which water flows continuously through the beads. The...

Full description

Saved in:
Bibliographic Details
Published in:Journal of fluid mechanics 2021-10, Vol.925, Article A8
Main Authors: Etzold, Merlin A., Linden, P.F., Worster, M. Grae
Format: Article
Language:English
Subjects:
Atmospheric pressure
Beads
Concentration gradient
Evaporation
Evaporation rate
Experiments
Fluid mechanics
Gradients
Humidity
Hydrogels
JFM Papers
Oil recovery
One dimensional models
Osmosis
Osmotic pressure
Polymers
Pressure head
Relative humidity
Reservoirs
Steady state
Transpiration
Water flow
Water reservoirs
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We present experiments and theory relating to transpiration through unrestrained hydrogel beads in contact with a water reservoir below and air above. Experimentally, we find that saturated hydrogel beads shrink until a steady state is reached in which water flows continuously through the beads. The size of the bead in steady state is sensitive to the evaporation rate, which depends on the relative humidity and speed of the surrounding air, and to the pressure head imposed by the fluid reservoir. Specifically, the bead size decreases with increasing pressure head or evaporation rate. Our one-dimensional model proposes that transport in the hydrogel is driven by gradients in osmotic pressure, caused by gradients in polymer concentration in the hydrogel that correspond to gradients in swelling. If the evaporation rate or the pressure head changes, the adjustment of this gradient requires the bead to change shape and size. Smaller beads have larger gradients of osmotic pressure, which drive higher transpiration rates and can draw water against larger pressure heads.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2021.608