Pöllmann Alexander, Reinelt Matthias, Briesen Heiko
Process Systems Engineering, TUM School of Life Science Weihenstephan, Technical University of Munich, Gregor-Mendel-Str. 4, 85354 Freising, Germany.
Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Str. 35, 85354 Freising, Germany.
Materials (Basel). 2022 Sep 1;15(17):6031. doi: 10.3390/ma15176031.
Mathematical models can provide estimates for the shelf life of water-sensitive products like food or pharmaceuticals. This study presents a simple kinetic model using two first-order reactions for the evaporation and condensation of water. Furthermore, the model can be simplified to contain only one free parameter, the reaction rate constant , which has been validated for silica gel at a relative humidity between 0% and 80% with experimental data. The experimental data shows the hysteresis effect of the silica gel in the region between 30% and 80% relative humidity and its dependence on the relative humidity earlier in the process. It also shows there are multiple equilibrium water contents at a relative humidity of 40%, depending on the previous relative humidity. The relative humidity barely influences the fitted reaction rate constant during adsorption. However, during the desorption process, not only the current relative humidity but also the history of relative humidity have an influence. A higher relative humidity in the previous step can slow down the desorption rate in the following step.
数学模型可以为食品或药品等对水敏感的产品的保质期提供估计。本研究提出了一个简单的动力学模型，该模型使用两个一级反应来描述水的蒸发和冷凝。此外，该模型可以简化为仅包含一个自由参数，即反应速率常数，该常数已通过实验数据在相对湿度为0%至80%的条件下对硅胶进行了验证。实验数据显示了硅胶在相对湿度30%至80%之间区域的滞后效应及其在此过程早期对相对湿度的依赖性。实验数据还表明，在相对湿度为40%时，根据先前的相对湿度不同，存在多个平衡水含量。在吸附过程中，相对湿度对拟合的反应速率常数几乎没有影响。然而，在解吸过程中，不仅当前的相对湿度，而且相对湿度的历史情况都有影响。上一步中较高的相对湿度会减慢下一步的解吸速率。
