Cryogenic freezers are commonly applied in the food processing and healthcare industries, and offer a highly effective preservation method without significant product degradation. The modelling of freezers has been conducted mainly around food processing, to observe the cooling rate during the chilling process. Typically, cryogenic freezers operate with a mix of air and nitrogen as the working fluid, with the effects on the heat transfer coefficient being thoroughly noted, in a range of applications. The effect of the heat transfer coefficient has not been investigated in a liquid nitrogen application, with a cryogenic applicability. This paper will focus on the CFD visualisation of the circulation of air around a lab scale cryogenic batch freezer. The effect of the heat transfer coefficient will be investigated in a number of scenarios, such as shelf loading conditions, product configuration and thermal profiles. The cryogenic batch freezer will be simulated in a range of room temperatures starting from -70°C, using a thermal profile which was obtained experimentally.

The rheological behavior of 34 commercial food dispersions was investigated and modeled with the Herschel-Bulkley model. Artificial neuronal networks (ANNs) were trained to predict the rheological parameters yield stress tau(0), consistency coefficient K and flow behavior index n in dependency of the composition of fats, carbohydrates, proteins and water. ANNs with 3 hidden layers and 2 neurons per layer showed good to very good results for all Herschel-Bulkley parameters. (c) 2012 Elsevier Ltd. All rights reserved.