Tailored surfaces for the mitigation of fouling in heat exchanger

In many heat exchangers an undesired layer forms on heat transfer surfaces, also known as fouling. This layer can lead to a drastic increase of the heat flux resistance and therefore resulting in decreased efficiency of the heat exchanger. Efforts towards avoidance or reduction of the occurrence of fouling most times lead to only limited success, and in such cases, typically require great effort to achieve such. A method to reduce fouling is an extension of the induction time by a defined modification of interfacial interactions between heat transfer surface and deposit. Because these interactions are caused by molecular and mechanical forces, two approaches for fouling mitigation have been developed: Modification of the energy related properties of the heat transfer surface Modification of the geometry related properties of the heat transfer surface. This work focuses on the realization of the first strategy. Therefore the induction period has to be explored in detai l to gain information about the conditions which favor a long induction period. In this period, the formation of stable crystals on the heat transfer surface and their compaction to a fouling layer take place. This process is mainly dependent on the interfacial free energy crystal/heat transfer surface. For many industrial applications of compact heat exchangers the only possibility to influence this energy is to modify the energetic properties of the heat transfer surface, i.e. its surface energy. To achieve this, different coating systems an coatings have been tested and examined concerning their energetic surface properties with respect to their performance when exposed to a saline solution in fouling experiments with a fouling test unit. All results were compared with standard stainless steel surfaces