Shape factors for the freezing time of ellipses and ellipsoids

doi:10.1016/0260-8774(91)90024-M

Journal of Food Engineering

Volume 13, Issue 3, 1991, Pages 159-170

https://doi.org/10.1016/0260-8774(91)90024-M Get rights and content

Abstract

By assuming that the freezing front is similar in shape to the surface, an expression is obtained for the shape factors of ellipses and ellipsoids. This expression agreed well with numerical results for the case of infinite Biot number but disagreed by up to 17% for intermediate Biot numbers. A curve-fitting expression is proposed that agrees with numerical results to within 6%.

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There are more references available in the full text version of this article.

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Chicken meat is among the most largely consumed meat worldwide. The shelf life of chicken meat is rather short so freezing is largely used to reduce water activity and stop the microorganism proliferation. In this paper experimental data available in the literature for food freezing, including poultry products, are briefly reviewed. Then, some new experimental measurements are presented for freezing of packed cylindrical chicken breast samples in air. The experimental freezing times were compared with the estimations of several semi-empirical or approximate models in the literature. Furthermore, by means of User Defined Functions for the implementation of the temperature-dependent thermophysical properties of chicken meat, the commercial CFD software package STAR-CCM + was used for analyzing the freezing process and estimating the freezing times of the tested specimens. For engineering purposes, it was decided to follow a simplified approach, by using an average value of the overall airside heat transfer coefficient. The numerical estimations were rather good (mean relative error −1.4% and mean absolute error 2.4%).
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A study of the literature published in recent years on freezing time prediction methods, with focus on simultaneous heat and mass transfer modelling is presented. Although models published vary from analytical simple equations to numerical methods, the most fruitful work is in finding simple equations for foods with regular shapes. It is difficult to develop more precise prediction methods for one-dimensional shapes as accurate experimental data are not easy to obtain. Heat transfer coefficients are hard to estimate with typical uncertainties of ±10–20% quoted and data on mass transfer coefficients are scarce. Research on the influence of thermal properties on the accuracy of models is useful. There are many models published for coupled heat and mass transfer for cooling, but very few models are available for freezing. Furthermore weight loss is an important factor for economic and quality reasons, therefore models should be developed in order to predict the weight loss during cooling and freezing.

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Shape factors for the freezing time of ellipses and ellipsoids

Abstract

Int. J. Refrig.

Int. J. Refrig.

Int. J. Refrig.

Int. J. Heat & Mass Transfer

J. Fd Technol.