Heat Transfer in Fluid Food Processing

Over the last decade the whole food chain, including the food processing industry, has been facing important technological challenges, mainly related to the need of attaining products of high quality and safety and of limiting, at the same time, the production costs. These challenges are nowadays also enforced by the continuous developments in the regulation related to the foods manufacturing processes. In this contest, food industry is required to innovate continuously in order to remain competitive. In this, like in other industrial fields, there is a growing awareness that the scientific research plays an important role in the dynamics of technological innovation. With regards to the food industry, it must be realized that, although the growing attention of the scientific community towards the problems related to the physical phenomena involved in the foods transformation processes, the technological improvements are growing slowly, if compared to other industrial fields. This is due to several reasons, among which the increasing competition between food firms which prevents the sharing of information and knowledge. Moreover, it must be observed that in the food industry the technological know-how is mostly based on experience and on uncodified knowledge which are difficult to transferred. Concerning the scientific aspect, it must be observed that different academic areas are involved in the applied research in food processing and not always the knowledge is fruitfully conveyed among them. All these aspects may prevent the innovation progress in this industrial field. The aim of the present chapter is to focus on a particular but important aspect of the various processes involved in the treatment of foods. The fundamental aspects of convective heat transfer, that is heat transfer occurring in flowing fluids, are discussed in relation to the problems of the food industry. In particular the forced convective heat transfer in single-phase system is addressed. First the fluid foods rheological and thermal characterisation is presented and discussed. The fundamentals of convection heat transfer are then briefly provided, together with the definitions of the relevant physical quantities and with the pertinent conservation equations. The following paragraph is particularly focused on the convective heat transfer in ducts with regard both to the Newtonian and non-Newtonian single-phase fluid flow. Being the optimization of the performances of the technological apparata and of the industrial plants a priority task of the applied research, the argument of the techniques which may be adopted to enhance the convective heat transfer mechanism is presented and discussed, with particular attention to the needs of the food industry.