Fouling by Milk and Dairy Product and Cleaning of Heat Exchange Surfaces

Abstract

Among processes of food engineering, heat transfer plays a key role. The use of heat exchangers is of such frequent occurence that they appeared in every step of industrial transformations and underwent a constant evolution. Different kinds of equipment, corresponding to specific use conditions according to concerned fields of using are available, among which, just to mention the best known ones: tubular exchangers, shell an tubes exchangers, plate heat exchangers, spiralflow exchangers, scraped surface exchangers and platular exchangers. Their function will be to transmit heat flux to one or between two fluids according to a given thermal specification. The principles of heat transmission are conduction, convection, evaporation, condensation and radiation, whatever the state of the involved fluids (gaz or liquid state) or changing phase in course of treatment. However, while flow and heat transmission in exchangers are now well-known phenomena in the simplest cases, fouling of surfaces remains one of the major problems not yet completely solved (47). This is especially true in the case of food liquids containing thermosensitive compounds such as milk, for example. Thus, in dairy industry, special attention and constant care are focused on thermal treatments and especially on sterilization processes.