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Food Science and Technology

Print version ISSN 0101-2061On-line version ISSN 1678-457X

Abstract

TERUEL, Bárbara; CORTEZ, Luís A.; LEAL, Paulo  and  LIMA, Antonio G. B.. THEORETICAL STUDY OF FRUITS COOLING WITH DIFFERENT FORMS GEOMETRICAL IN THE FORCED-AIR SYSTEM. Ciênc. Tecnol. Aliment. [online]. 2001, vol.21, n.2, pp.228-235. ISSN 0101-2061.  http://dx.doi.org/10.1590/S0101-20612001000200019.

This paper presents a numerical study for obtaining cooling curves of orange Valência (Citrus sinensis O.) and banana Prata (Mussa Balbisiana Colla), in different positions along the bed and conditioned in package with 40% of effective opening area. The fruits were pre-cooled in a forced-air system (1.933m3/h), at 1°C and 7°C, RH= 88,4 ± 2,0% and air velocity around 1m/s. A two-dimensional mathematical model was applied, assuming prolate spheroid coordinate, to characterize the transient heat transfer process inside the fruits considering convective profile conditions at the surface of the body. The generated equations were numerically solved by finite-volume method. The convective heat transfer coefficients were obtained using the least square method by comparison between experimental and numerical data. The comparative analysis of the theoretical and experimental curves presented a satisfactory agreement, with error between 5% and 7%. It was noted that the convective heat transfer coefficient changes with the fruits position in the bed and cooling time present a variation of approximately 38% among the different points. The spatial distributions of temperature inside the fruits, for three times, demonstrate the existence of a temperature differential between the center and the surface of 30%, approximately. The model predicts that the cooling rate is in the extremes of the banana. The Bi and Fo numbers obtained represent very well the heat transfer process in the fruits under different relationships of volume/area.

Keywords : orange; banana; numerical; finite-volume.

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