Direct measurement of the mass transport coefficient of water in silica-gel using the zero length column technique
Direct measurement of the mass transport coefficient of water in silica-gel using the zero length column technique
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DOI：
10.1016/j.energy.2021.121945
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发表时间：
2022-01
期刊：
影响因子：
9
通讯作者：
S. Brandani;E. Mangano
中科院分区：
文献类型：
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作者：
S. Brandani;E. Mangano
在所有低品位热驱动的硅胶吸附过程中，水在硅胶上的吸附动力学对于优化设计非常重要，并且成为超低品位热应用的关键因素。本文提出了一种测定商业硅胶中水的传质系数的新方法，并利用零长柱技术对单个颗粒进行了测量。在平衡条件下，该方法提供了在不到一天的时间内获得数千个点的平衡等温线的关键优势。这样就可以通过数值插值得到蒸汽浓度与平衡吸附量之间的关系。在较高的流量下，系统在动力学控制下运行，因此可以确定传质系数。该方法无需使用特定模型即可计算从测量信号中获得传质系数所需的所有元素。在不同的流量和三种不同的温度下进行了吸附和解吸实验。动力学响应可以用来确定平均传质系数，这与文献值一致，但观察到一个复杂的行为，表面扩散是传递过程的主要贡献。
In all silica-gel adsorption processes driven by low-grade heat, the kinetics of adsorption of water on silica-gel is very important in order to optimize design and becomes an essential factor in ultra-low grade heat applications. A new approach for the determination of the mass transfer coefficient of water in commercial silica-gel is proposed and demonstrated with measurements on a single particle using the zero length column technique. Under equilibrium conditions the methodology offers the key advantage to acquire equilibrium isotherms with thousands of points in less than one day. This allows to obtain the relationship between vapour concentration and equilibrium adsorbed amount through numerical interpolation. At higher flowrates, the system operates under kinetic control therefore allowing the determination of the mass transfer coefficient. The novel approach calculates all the elements needed to obtain the mass transfer coefficient from the measured signals without the need to use a specific model. Adsorption and desorption experiments were carried out at different flowrates and three different temperatures. The kinetic responses can be used to determine an average mass transfer coefficient, which is consistent with literature values, but a complex behaviour is observed with surface diffusion as the main contribution to the transport process.