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This study is focused on the effects of starch gelatinisation on heat exchange in food systems containing four modified starch concentrations (0, 2, 6 and 10%). Viscosity profiles of samples were experimentally measured: the effect of gelatinisation was evident, particularly at 6% and 10%, where the viscosity increased from 0.010 to 70 Pa s and to 1507 Pa s, respectively. The heat exchange rate showed a decrease with the increasing of starch concentration, and the effects were observed until 6%. Four Computational Fluid Dynamics (CFD) models were also developed, experimentally validated (RMSE < 1.5°C) and used to study the heat exchange. Velocity profiles showed that the convective flows slowed down from 2.5 to 0 mms À1 after the gelatinisation. Finally, the effects on the slowest heating/cooling zone (SHZ/SCZ) location in the CFD models were studied: at 0% and 2%, the SHZ settled 15 and 80 mm from the bottom of jars in heating and cooling phase, respectively. At 6% and 10%, before the starch gelatinisation phase, the SHZ was located in a similar position of the 0% and 2% while when the gelatinisation occurred the SHZ slightly moved towards the geometric centre (50 mm) as for an only-conductive product. CFD of heat exchange in starch food systems M. Cordioli et al. 855 CFD of heat exchange in starch food systems M. Cordioli et al. CFD of heat exchange in starch food systems M. Cordioli et al. CFD of heat exchange in starch food systems M. Cordioli et al. CFD of heat exchange in starch food systems M. Cordioli et al. CFD of heat exchange in starch food systems M. Cordioli et al.

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The objective of this study was to develop and experimentally validate CFD models of thermal treatments on whey protein dispersions both in batch and continuous conditions, considering several processing times (2 to 9.92 min), shear rates (191 to 519 s−1) and temperatures (70, 80 and 85 °C). Regarding thermo-rheological properties of WP dispersions, the viscosity peak (raising up at 66 °C) decreased as the shear rate increased. Two different CFD models were developed to simulate the thermal process: results showed a good fitting between experimental and simulated data (RMSE <1.7 °C for batch model and mean temperature difference of 0.93 °C for the continuous one). Based on the developed models, cook values of both processes were calculated and slowest heating points were exactly located; by means of these data, equations to estimate the cook value in processing conditions within experimental range were obtained, overcoming the need of experimental tests or in-silico simulations.

In the present work, temperature distribution within an industrial blast chiller with pork leg for Protected Designation of Origin Parma ham production was studied and the slowest cooling zone and the fastest cooling zone were recognized. Moreover, apparent heat transfer coefficients in both positions were calculated and resulted equal to 27.1 and 15.6 W m -2°C-1 , respectively. A finite element method model by distinguishing the three main components (skin, lean meat and bone) of the leg for the unsteady heat transfer during cooling was developed and validated against industrial chiller data. Good agreement between experimental and simulated data was obtained with RMSE value for thermal centre equal to 0.81°C. Furthermore, in order to introduce CCP limit in the HACCP plan, a microbial growth model of the most important pathogens in meat was developed starting from the heat transfer model results. Temperature as well as pathogen growth were estimated in the case of different plant breakdowns. Defined CCP limit was represented by reaching 11°C at 5 mm of depth within 2 h from the beginning of the cooling process, moreover a different cooling program was simulated and established as the alternative one.

In this work, the performance of a plate heat exchanger with rectangular, rhombus, and elliptical vortex generators with 3, 5, and 7 mm width and 3, 6, and 9 mm height were investigated by means of computation fluid dynamics (CFD). Moreover, seven flow rates (from 0.01 to 1 ms −1 ) were tested and 196 CFD models were obtained.Heat transfer coefficient, pressure drop, Colburn j, and Fanning f factor were considered to evaluate the performance of the heat exchanger. The best heat exchange was obtained for rhombus wings and the highest Colburn j factor was obtained for 7 mm width and 6 mm height. The lowest pressure drop was obtained for 3 mm width and 3 mm height elliptical wings. Regarding surface reduction, the best result for all the geometries was with 5 mm width and 9 mm height, allowing a possible reduction of 25, 26, and 23% for rectangular, rhombus, and elliptical geometry. Practical applicationsPlate heat exchangers are extensively used for continuous thermal processing of liquid foods without particles in suspension and with low viscosity. In the last decades, due to the increasing demand of high quality foods and energy saving, increasing the overall heat transfer performances of food processes became crucial for the sector. Computation fluid dynamics (CFD) technique can contribute to understanding food fluid flows inside heat exchangers and in supporting equipment design. Product and process quality can be improved with minimum cost and time investment. In this work CFD was used for studying the performances of a plate heat exchanger with different passive vortex generators presenting different shapes and dimensions. The simulated data allowed identifying the best geometry with the best balance between heat performance improvements and pressure losses. The proposed approach successfully applied to Newtonian fluid could be extended also to non-Newtonian liquid foods and to different plate heat exchanger design.