Schugmann Martin, Foerst Petra
Institute of Process Systems Engineering, Technical University of Munich, Gregor-Mendel-Straße 4, 85354 Freising, Germany.
Rev Sci Instrum. 2022 Jun 1;93(6):065108. doi: 10.1063/5.0083295.
This paper describes the technical setup and validation of a thin film drying device in which the conditions such as air temperature, relative humidity, and velocity can be controlled in the range of 20-200 °C, 0-1.5 m s, and vapor mass flows up to 1200 g min. For the first time, it is possible to perform in situ manipulation of the drying kinetic in a highly dynamic manner. The setup allows for a precise online determination of drying and rehydration kinetics; the recording of relevant process parameters such as air humidity, air and surface temperature; and the monitoring of optically observable material properties. The concept for rapid real-time changes in drying conditions is explained, and the constructive details are elucidated. Highly precise gravimetry by a proposed measurement methodology and simultaneously avoiding condensation during rapid parameter changes is accomplished. This is achieved by the combination of minimized thermal inertia of the system, air conditioning via carrier gas-free evaporation, and a highly responsive active insulation. The influence on the drying kinetics by temperature, humidity, and air velocity is shown with experiments on aqueous maltose solution, and the experimental precision is validated. The validation showed a high grade of accuracy regarding gravimetric determination with a maximum observed mass difference of 0.21% referring to the dried product. The dynamics of the setup under in situ changes in drying conditions is exemplified by further experiments. In addition, the presented setup for the first time enables the real time manipulation and observation of kinetically coupled processes such as crystallization behavior, morphology formation, or material degradation during drying. Therefore, it has important practical value for the development of efficient and energy-saving drying methods and products with specific, tailor-made properties.
本文描述了一种薄膜干燥装置的技术设置和验证，该装置中空气温度、相对湿度和速度等条件可在20 - 200°C、0 - 1.5 m/s以及高达1200 g/min的蒸汽质量流量范围内进行控制。首次能够以高度动态的方式对干燥动力学进行原位操作。该设置允许精确在线测定干燥和复水动力学；记录相关过程参数，如空气湿度、空气和表面温度；以及监测光学可观察的材料特性。解释了干燥条件快速实时变化的概念，并阐明了结构细节。通过所提出的测量方法实现了高精度重量法，同时在快速参数变化期间避免了冷凝。这是通过系统最小化热惯性、通过无载气蒸发进行空气调节以及高响应性主动隔热的组合来实现的。通过对麦芽糖水溶液的实验展示了温度、湿度和空气流速对干燥动力学的影响，并验证了实验精度。验证表明重量测定具有高精度，相对于干燥产品观察到的最大质量差为0.21%。通过进一步的实验举例说明了干燥条件原位变化下该装置的动态特性。此外，所展示的设置首次能够实时操作和观察动力学耦合过程，如干燥过程中的结晶行为、形态形成或材料降解。因此，它对于开发高效节能的干燥方法以及具有特定定制特性的产品具有重要的实际价值。
