Article

A model to design high-pressure processes towards an uniform temperature distribution. J Food Eng

Department of Applied Mathematics, Facultad de Matemáticas, Universidad Complutense de Madrid, Ciudad Universitaria, s/n, 28040 Madrid, Spain
(Impact Factor: 2.77). 02/2007; 78(4):1463-1470. DOI: 10.1016/j.jfoodeng.2006.01.020

ABSTRACT

A mathematical model has been developed to describe the phenomena of heat and mass transfer taking place during the high-pressure treatment of foods. It has proved that convection currents in the pressure medium play an important role in the thermal evolution of the processed samples especially when the filling ratio in the pressure vessel is low. This model shows to be an extremely useful toot to design high-pressure processes seeking a uniform temperature distribution. (c) 2006 Elsevier Ltd. All rights reserved.

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• "The two-dimensional CFD simulations of Otero et al. (2007) found that the filling ratio of the HP vessel played a major role in process uniformity, with convective currents having least effect on heat transfer when this ratio is large. Otero et al. (2007) also showed that by anticipating the temperature increase resulting from compression heating and by allowing the pressure transmitting medium to supply the appropriate quantity of heat, the uniformity of HPP was enhanced when both large and small sample ratios were used. More recently, Abdul Ghani and Farid (2007) used threedimensional CFD simulations to illustrate both convective and conductive heat transfer in a HPP system loaded with pieces of solid beef fat. "
Article: Computational Fluid Dynamics in the Design and Analysis of Thermal Processes: A Review of Recent Advances
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ABSTRACT: The design of thermal processes in the food industry has undergone great developments in the last two decades due to the availability of cheap computer power alongside advanced modelling techniques such as computational fluid dynamics (CFD). CFD uses numerical algorithms to solve the non-linear partial differential equations of fluid mechanics and heat transfer so that the complex mechanisms that govern many food-processing systems can be resolved. In thermal processing applications, CFD can be used to build three-dimensional models that are both spatially and temporally representative of a physical system to produce solutions with high levels of physical realism without the heavy costs associated with experimental analyses. Therefore, CFD is playing an ever growing role in the development of optimization of conventional as well as the development of new thermal processes in the food industry. This paper discusses the fundamental aspects involved in developing CFD solutions and forms a state-of-the-art review on various CFD applications in conventional as well as novel thermal processes. The challenges facing CFD modellers of thermal processes are also discussed. From this review it is evident that present-day CFD software, with its rich tapestries of mathematical physics, numerical methods and visualization techniques, is currently recognized as a formidable and pervasive technology which can permit comprehensive analyses of thermal processing.
Critical reviews in food science and nutrition 01/2013; 53(3):251-75. DOI:10.1080/10408398.2010.518256 · 5.18 Impact Factor
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• "These losses have been estimated to be more than 40 to 50% in the tropics and subtropics. Post-harvest losses of fruits and vegetables in developing countries is therefore of serious concern (Otero, Ramos, Elvira &Sanz, 2007). Moreover, in many developing countries only a limited quantity of fruit and vegetable products are produced for local markets or for exportation due to lack of machinery and infrastructure. "
Article: Thermal Diffusivity Variations of Potato during Precooling in Natural Convection Environment
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ABSTRACT: The present work is development of a simple method to evaluate the skin temperature and thermal diffusivity variations of regular shaped food products subjected to natural convection cooling at constant pressure. Experimental investigations were carried on the sample chosen (potato), which is approximately of spherical geometry. The variation of temperature within the food product is measured at several locations from center to skin, under natural convection environment using a deep freezer, maintained at -10°C. Skin temperature is obtained based extrapolation of temperature profile from center towards skin. Thermal diffusivity variation iscalculated using one-dimensional Fourier’s equation and is plotted against skin temperature of the product.
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• "This has been confirmed to be true in Otero et al. (2007), by validation with several comparisons between numerical and experimental results. In Otero et al. (2007) they show that when the filling ratio of the food inside the vessel is not much higher than in the pressurizing medium, the solution of this model differs a lot from the experimental results. Therefore they improve the model by including convection effects in the pressurizing medium. "
Article: Generalized enthalpy model of a high-pressure shift freezing process
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ABSTRACT: High-pressure freezing processes are a novel emerging technology in food processing, offering significant improvements t the quality of frozen foods. To be able to simulate plateau times and thermal history under different conditions, in thi work, we present a generalized enthalpy model of the high-pressure shift freezing process. The model includes the effect of pressure on conservation of enthalpy and incorporates the freezing point depression of non-dilute food samples. In addition the significant heat-transfer effects of convection in the pressurizing medium are accounted for by solving the two-dimensiona Navier–Stokes equations. We run the model for several numerical tests where the food sample is agar gel, and find good agreemen with experimental data from the literature.
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