Modeling of fouling in a bench-scale plate heat exchanger system during milk pasteurization

Milk processing is an important example of fouling in the food industry. Thermal instability of milk causes formation of solid fouling deposits as a result of specific reactions of milk components. Flow rate and inlet stream temperatures are two of the key operational factors affecting fouling behavior. In this study, a fouling model using FLUENT was developed for different inlet milk temperatures and flow rates. The results were compared with experimental data from a bench-scale plate-type heat exchanger. It was found that there was up to 50% less deposit formation when the inlet milk temperature was higher with minimal effect milk flow rates studied. Calculated amount of deposit based on thermal performance change due to fouling was in good agreement with measured values. Percent differences were in the range of 0.9 to 9.2% for flow rates and inlet milk temperatures studied. The difference between the calculated and measured deposit amounts was highest (34.2%) for high flow rate and high temperature test condition. Using this model, fouling on the heat exchanger surfaces at different test conditions can be predicted with reduced number of experiments.