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Abstract: In the previous paper (Part I) of this series, mathematical models of airflow and heat transfer inside ventilated packaging systems were developed and presented based on the porous media approach. In the present paper (Part II), we describe the CFD methods used to solve the mathematical models for both layered and bulk packaging systems, and the structure of a user-friendly software package (called ‘CoolSimu’) that integrates the modeling system. We also present the results of several simulation tests for both layered cartons and bulk bins of fruit undergoing forced-air cooling. Overall, the CFD modeling system gave satisfactory predictions of temperature profiles of fruit. When model predictions and experimental product center temperature data were compared, good agreements were obtained. The lack of fit at certain locations inside the packaging was attributed to inaccurate temperature measurement and uncertainties in model input data. [Copyright &y& Elsevier]

Abstract: The paper deals with modeling the convective drying process. A relevant and reliable mathematical model that captures the history and distribution of temperature is presented. The attention is focused on the simultaneous heat and mass transfer occurring during drying where dry and hot air flows about the food. In the present study, external resistance to mass transfer is considered negligible. As a result, the drying curve is almost independent of the boundary conditions, which means that drying is diffusion-controlled. The main connotation of present study regards to undertake analytical procedure to establish the novel model for practical applications. The results show that the temperature evolution can be evaluated from an advanced analytical solution in a quick and efficient manner. The model is validated with the literature experimental data obtained for carrot and mango slabs. A good agreement is obtained between the model predictions and the available experimental results. [Copyright &y& Elsevier]

Abstract: Acrylamide formation in a food model during frying can be analyzed in space and time with a traditional heat and mass transfer approach. In this paper a joint simulation/experiment approach has been exploited: the computational fluid dynamics has been coupled to chemical kinetics, to describe concentration and temperature fields in a food substrate, subject to interdependent and non-uniform heat and mass transfer, while validating measurements have been performed by high performance liquid chromatography. A multi-objective SIMPLEX optimization has been finally employed for the overall model tuning, incorporating all phenomenological variations. The numerical results confirmed that the acrylamide formation is non-linearly dependent on the operating thermal regime, in general more than doubling its average levels when the process temperature is increased by 10% only. Based on the proposed acrylamide maps, a maximum concentration locus is found on the product’s upper corner, depending on the specific transport ensemble and therefore on the local process conditions. For potato frying at an initial temperature of 190°C, the maximum local acrylamide level after 4min (almost 4×10−2 mg/g) is almost four times the one obtained when frying at 170°C, while scaling only linearly with process duration. [Copyright &y& Elsevier]

Abstract: In this paper, we apply two mathematical tools for the analysis of models describing heat and mass transfer in dispersed systems, namely scale analysis and integral approximation. The particular model investigated is a 1-D model describing the cooling of packed beds of fresh agricultural produce using the porous media approach. With scale analysis, one can determine relevant terms in the model and subsequently one can make justified approximations. Traditionally, in the porous media approach one assumes that temperature gradients in individual products are negligible, as expressed by the Biot number Bi <0.1. By means of the integral approximation method, we have shown that the porous medium approach can be extended to the range Bi <10 via the definition of an internal heat resistance. Via the integral approximation method, we have calculated the internal resistance for a variety of products having simple geometries. Scale analysis shows that for the problem investigated, there are two regimes, depending on whether solid and fluid phase are in so-called local thermal equilibrium. [Copyright &y& Elsevier]

Abstract: This paper introduces a general computational model for beer pasteurization tunnels, which could be applied for any pasteurization tunnel in the food industry. A simplified physical model, which combines fundamental and empirical correlations, and principles of classical thermodynamics, and heat transfer, is developed and the resulting three-dimensional differential equations are discretized in space using a three-dimensional cell centered finite volume scheme. Therefore, the combination of the proposed simplified physical model with the adopted finite volume scheme for the numerical discretization of the differential equations is called a volume element model, VEM [Vargas, J. V. C., Stanescu, G., Florea, R., & Campos, M. C. (2001). A numerical model to predict the thermal and psychrometric response of electronic packages. ASME Journal of Electronic Packaging 123(3), 200–210]. The numerical results of the model were validated by direct comparison with actual temperature experimental data, measured with a mobile temperature recorder traveling within such a tunnel at a brewery company. Next, an optimization study was conducted with the experimentally validated and adjusted mathematical model, determining the optimal geometry for minimum energy consumption by the tunnel, identifying, as a physical constraint, the total tunnel volume (or mass of material). A parametric analysis investigated the optimized system response to the variation of total tunnel volume, inlet water temperature, production rate, pipe diameter and insulation layer thickness, from the energetic point of view. It was shown that the optimum tunnel length found is ‘robust’ with respect to the variation of total tunnel volume, combining quality of the final product with minimum energy consumption. The proposed methodology is shown to allow a coarse converged mesh through the experimental validation of numerical results, therefore combining numerical accuracy with low computational time. As a result, the model is expected to be a useful tool for simulation, design, and optimization of pasteurization tunnels. [Copyright &y& Elsevier]