CFD-Framework for Prediction of Thermally-Driven Fouling Layer Buildup in Micro-Channels

Industrial milk pasteurization processes are often accompanied by thermally-driven fouling layer growth, which impairs heat transfer and reduces system efficiency. To mitigate this, macro-scale heat exchangers are typically employed, as they are less susceptible to fouling than their micro-scale counterparts. Nevertheless, micro-structured heat exchangers offer superior temperature control and the potential for enhanced process efficiency as a result of increased transfer rates. To understand the underlying mechanisms of whey protein fouling at the micro-scale, combined numerical and experimental investigations are conducted. A model within an OpenFOAM framework is developed to predict the whey protein fouling process in rectangular micro-channels through CFD simulation, considering the direct formation and growth of fouling layers at micro-channel walls. The fouling is modeled as a chemical reaction through Arrhenius equations, where the species concentrations for folded and unfolded proteins are transported passively. The reaction rate is based on the local concentrations and temperature, and the reaction leads to the formation of a solid layer in the fluid domain. ... mehrAn Immersed Boundary Method (IBM) with conjugate heat transfer is used to model the effect of the solid layer on the velocity and temperature field. Results for a 1 x 1 x 100 mm channel with a heated bottom section show that fouling layer growth starts at the edges where the surface-to-volume ratio is high, and that fluid blockage influences the layer shape, since a higher average velocity leads to more removal and thus slower layer growth.