Modelling of fouling in a plate heat exchanger with high temperature pasteurisation process

Abstract

This article discusses the steady-state and transient performances of continuous High-Temperature-Pasteurisation-Process (HTST) - milk plant. The plant comprises of integrated three-stage sections (regeneration, heating and cooling) counter-current gasketted-Plate-Heat-Exchanger (PHE) along with holding-tank, boiler, chiller unit and holding-tube. The conservation of mass and energy principle is applied in modelling the plant. Modelling of heat-exchanger is improved using Log-Mean-Temperature-Difference (LMTD) approach. Using this approach, where a rise of about 1 °C has been observed in the temperature of the heat-exchanger’s heating section, and the transient representation of heat-exchanger is thus improved. Fouling is a major issue in a dairy industry, as it incurs additional energy and cost. Moreover, problems due to fouling of exchangers lead to abnormal flow and temperature profile. This makes the pasteurisation difficult to control. Thus, fouling prediction is vital in grass-root design and even more, in retrofit applications. Therefore, the dynamic-behavior of the plant is also augmented by introducing one-dimensional predictive fouling-model (around a thickness of 2.8 x 10-5 m) in the overall integrated plant. It is observed that the reduction of 0.5 °C in pasteurised milk temperature approximately, reduces the quality of milk. The dynamic-model of HTST process is validated with experimental plant data. The sensitivity analysis of the model is also presented. The results of the integrated model are useful in constructing a good control strategy to improve the overall performance, reliability, efficiency, quality-control and economic benefits of the dairy farm.