Cleaning mechanisms of immerged systems

受污染有机物在换热表面的清洗过程是一个复杂的界面相互作用、传质、换热、流体力和化学反应相互作用的过程，目前对其认识还不够充分。本研究项目的主要目的是了解浸没系统清洗过程中的因果关系。采用WPI凝胶形式的乳清蛋白作为典型的污垢模型。本研究项目分为三个部分。第一部分包括与清洗过程相关的所有材料特性的调查，特别是强度、粘弹性特性、扩散系数、表面形貌、附着力和内聚力。这些材质参数将在项目的第二部分中使用。在这里，将建立污垢层连续力学有限元模型的基础数据库。采用流固耦合模型(FSI)对流体相进行模拟，从而模拟WPI的清洗过程。为了验证和改进FSI模型，第三部分使用了两种已有的方法，即流体动力学测量(FDG)和局部磷光检测(LPD)。FDG方法可以研究清洗过程的三个阶段，膨胀阶段、均匀阶段和腐烂阶段。与粒度分析仪相结合，可以确定去除的颗粒的粒度。利用LPD方法，可以在层流和湍流条件下局部确定不同流型的清洗时间。通过比光强和污垢层厚度的相关关系，可以量化除污率以及污垢层厚度的变化。建模方法将进一步发展，并基于该FSI模型设计和验证定制的、特定于系统的清洁策略。此外，将有完善的方法学方法可用，然后可应用于任何污垢层。

The cleaning process of fouled organic material on heat transfer surfaces is a complex interaction of interfacial interactions, mass transfer, heat transfer, fluid forces and chemical reactions, which is not fully understood at present. The main objective in this research project is to achieve a fundamental knowledge of the cause-effect relationships in the cleaning of immersed systems. Whey protein in the form of WPI gel are to be used as a representative model fouling system. The research project is divided into three parts. The first part comprises the investigation of all material properties which are relevant for a cleaning process, specifically strength, viscoelastic characteristics, diffusion coefficient, surface topography, adhesion and cohesion force. These material parameters will be used in the second part of the project. Here a fundamental data base for a continuum-mechanical FEM model of the fouling layer will be set up. The fluid phase will be simulated with a fluid-structure interaction model (FSI) model, so that the cleaning process of WPI can be simulated. To validate and improve the FSI model, two established methods, namely fluid dynamic gauging (FDG) and local phosphorescence detection (LPD), are used in the third part. The FDG method enables to investigate the three stages of the cleaning process, swelling stage, uniform stage and decay stage. In combination with a particle size analyzer the particle size of removed particles can be determined. With the LPD method, it is possible to locally determine the cleaning time in different flow geometries under laminar and turbulent flow conditions. By correlation of the specific light intensity and the fouling layer thickness a removal rate as well as a change of the layer thickness can be quantified. The modeling approach will be developed further and based on this FSI model a tailored and system-specific cleaning strategy can be designed and validated. Furthermore well-established methodological approaches will be available, which can then be applied to any fouling layer.