Microwave assisted freezing part 1: Experimental investigation and numerical modeling |
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| Affiliation: | 1. Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, 44-100 Gliwice, Poland;2. Norges Teknisk-Naturvitenskapelige Universitet, Kolbjø rn Hejes Vei 1D, Trondheim 7049, Norway;1. Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;2. Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea |
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| Abstract: | The aim of this study was to develop an innovative process dedicated to enhancing the quality of frozen food using microwaves. A microwave assisted freezing device was designed at the laboratory scale to perform experiments in controlled conditions. Small samples of methylcellulose gels were frozen using nitrogen gas in a TE10 waveguide, where microwaves at 2.45 GHz were emitted intermittently or continuously. A numerical model was also developed to obtain results difficult to measure such as the local electric field and the corresponding energy density. The phase change part of the model was based on an enthalpy formulation and on the growth of spherical ice crystals. An original “hybrid 2D-3D” solving methodology was used to reduce the duration of the simulations. Favourable comparisons between the predicted temperatures and the experimental data highlighted the relevance of the models used for the thermophysical and dielectric properties. The analysis of the interactions between microwaves and matter, performed with numerical simulations, revealed the role of the freezing front as a boundary. The strong influence of sample size and of dielectric properties on the power density distribution were also illustrated when comparing our results with those published previously. The scientific knowledge obtained through this study and the original structure of the numerical model will be used to optimize microwave assisted freezing and link the process parameters to the reduction of ice crystal size highlighted in the companion paper.Industrial relevanceMicrowave assistance during freezing can improve frozen product quality by reducing ice crystal size. This innovative and promising process has not yet been given much attention. Developing an accurate model which describes microwave – matter interactions during phase change permits numerical simulations that can facilitate the design of industrial equipment, and determine optimal product dimensions. |
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