Transpiration through hydrogels
Transpiration through hydrogels
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DOI：
10.1017/jfm.2021.608
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发表时间：
2021-08-23
影响因子：
3.7
通讯作者：
Worster, M. Grae
中科院分区：
文献类型：
--
作者：
Etzold, Merlin A.;Linden, P. F.;Worster, M. Grae
我们目前的实验和理论，通过不受限制的水凝胶珠与下面的水库和上面的空气接触蒸腾。实验上，我们发现饱和的水凝胶珠收缩，直到达到稳定状态，其中水连续流过珠。稳定状态下的珠粒的尺寸对蒸发速率敏感，蒸发速率取决于周围空气的相对湿度和速度，并且对流体储存器施加的压头敏感。具体地，珠粒尺寸随着压头或蒸发速率的增加而减小。我们的一维模型提出，水凝胶中的运输是由渗透压梯度驱动的，渗透压梯度是由水凝胶中的聚合物浓度梯度引起的，其对应于溶胀梯度。如果蒸发速率或压头改变，则该梯度的调节需要珠改变形状和尺寸。较小的珠粒具有较大的渗透压梯度，其驱动较高的蒸腾速率，并且可以对抗较大的压头汲取水。
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.