The application of highly effective microstructured devices in continuous production and industrial environments is frequently prone to fouling. A new method is presented to characterize fouling in these microstructures. Thermal fouling of aqueous solutions containing whey protein were used as a test system. Different fouling effects could be observed and distinguished. Integral fouling indicators, such as thermal fouling resistance and pressure drop, as conventional criteria for the occurrence of fouling were compared with direct local optical observation. Low thermal fouling resistances could be detected.

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Microstructured heat exchangers typically comprise a number of parallel microchannels with inlet and outlet headers. The uniformity of flow rates among the parallel microchannels is governed by the field of fluid pressure in the system. This contribution presents, three dimensional (3D) CFD simulations performed using OpenFOAM (Open-Source Field Operation and Manipulation) by employing simpleFOAM solver to investigate flow distribution in an array of four parallel microchannels with a hydraulic diameter of 500 µm each. The working fluid is water and an incompressible, single-phase flow is assumed. The maldistribution is induced by complete or partial blockage of single microchannels in different scenarios. Both number of blocked microchannels and position of the blockage inside the channel array are altered.The results show the effects of induced blockage on the fluid flow distribution in the parallel microchannels. The standard deviation of flow distribution not only depends on the total number of the blocked microchannels but also on their position inside the flow array. For validating CFD results, pressure drop and flow distribution are also investigated through various experiments. Therefore, pressure drop measurements for different scenarios are conducted. A good agreement between simulation and experiment is observed. Simulation studies reveal that the free cross-section is not the governing criterion for both flow distribution and heat exchange. Fouling on the hot surface more strongly influences the outlet temperature than completely blocked channels.The contribution shows that even with a relatively simple model, interesting effects in microstructured heat exchangers can be found, allowing for a deeper understanding of the specific properties of micro structures.