A 2D fouling model for milk pasteurizer using plate heat exchangers (PHEs) was implemented and validated. The model emphasis was placed on fouling prediction based on the hydrodynamic and thermodynamic performances of PHEs in 2D environment. Different types of multichannel PHEs, i.e. 12-channel PHE 1 and 20-channel PHE 2 with both counter-current and co-current flows were applied to validate the model by visualization and quantification of milk deposit developed in the fluid channels. The predicted mass deposit values at each channel were in good agreement with the experimental data with the average prediction error of 0.4 g or 10.9% (R-2 = 0.98) for PHE 1. The theoretical values of temperature and mass deposit for a plate of PHE 2 were closer to the actual measurements with errors of 1.6 degrees C or 2.1% and 0.06 g or 6%, respectively. The aggregation rate of unfolded protein was observed to increase exponentially with increasing wall temperature, due to a reduction in flow rate and heat transfer coefficient. The predicted milk deposit distribution on the plate surface is expected to determine the sensor location appropriate for on-line monitoring and furthermore, optimization of the thermal process for minimizing milk fouling. (c) 2005 Elsevier Ltd. All rights reserved.