The optimisation of heat treatment processes in the dairy industry is of high practical interest. Models are key to understanding and optimising equipment design, operating conditions, energy and water utilization, heating and cleaning cycles and economics. Decades of research have led to the development of many models, however, there is still a lack of understanding about the role and mechanism of denaturation and deposition of proteins from whey solutions. Extensive validation of the more recent thermal and fouling models against experimental data is also incomplete. Here, five sets of detailed data from dynamic experiments in typical Plate Heat Exchangers (PHEs) are used to validate a 2D-distributed, dynamic model under fouling. The model accounts for the exchanger geometry, operating conditions and prevailing local conditions. Three reaction mechanisms for β-lactoglobulin (β-LG) protein unfolding, aggregation and deposition are considered, one of which is novel.First, a validation was carried out of the thermal PHE model alone (i.e. under clean conditions, with no fouling) against a water-water dynamic experiment, with excellent results. The exit temperatures predictions match the experimental observations within <1C on average. The fouling model was then validated against four dynamic water whey protein solutions (WPS) experiments (hot water heating a cold WPS stream)covering different conditions. Some of the model deposition constants were obtained through parameter estimation. Comparison of predicted and measured quantities (exittemperatures and amount of deposit in each channel at the end of the experiments) showthat neither the aggregate protein deposition model nor the unfolded deposition model on their own can describe the observations. It is shown that a new modification that combines both mechanisms results in an improved fitting of the data in all experiments. The combined deposition scheme results indicate that both mechanisms are important in different parts of the exchanger, and even along individual plates.