Effect of fouling on falling film evaporator performance in industrial conditions of fruit juice concentrate production

Abstract

In food processing, falling film evaporators are commonly used and their energy consumption is a significant operating cost for the production of juice concentrate. This cost is influenced not only by the evaporator design but also by the method of operation, particularly the fouling of the heat exchanger walls formed during the operation of the evaporator on the inner surface of the tubes from the juice side. These deposits are a significant component of the total wall thermal resistance, thus hindering evaporation. This issue results in a production decrease and requires evaporator cleaning. The publication presents an analysis of the calculation methods of fouling formation and their thermal resistance based on a literature review on evaporators for the production of sugar and milk. The obtained results were then processed by adjusting the coefficients to the experimental results obtained during the actual production of fruit juice concentrate. The decrease in actual evaporator efficiency was used to experimentally verify the theoretical calculations. This analysis resulted in a final simple formula for the estimation of the fouling influence on evaporator performance under industrial conditions. Simulations have shown that a sharp drop in evaporator efficiency may occur with insufficient recirculation or prolonged operation without cleaning. In this case, the amount of sediment can increase and cause a change in the boiling character and thus a rapid decrease in evaporation. • Effect of fouling on falling film evaporator for fruit juice concentrate production is estimated. • Fouling build-up speed on the inner surface of the tubes for fruit juice concentrate production is estimated. • Industrial fouling conditions in the production of fruit juice concentrate are analysed.