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