naa a22 4500 510724175 CHVBK 20180411082929.0 cr unu---uuuuu 180411e20130101xx s 000 0 eng 10.1007/s11947-011-0757-6 doi (NATIONALLICENCE)springer-10.1007/s11947-011-0757-6 Non-uniform Heat Transfer During Air-Blast Freezing of a Fruit Pulp Model in Multilayer Boxes [Elektronische Daten] [Jaime de Resende, Mônica Prado, Vivaldo Junior] Effective heat transfer coefficients were measured using an aluminum test body and compared with the results obtained from a Gnielinski correlation for air-blast freezing of a fruit pulp model in multilayer boxes, with the internal airflow through rectangular ducts and the hydraulic diameter as characteristic dimensions. The quantities of products inside the boxes were varied, and the inlet air velocities and temperature profiles during freezing were measured. The inlet air velocities were applied in dimensionless Gnielinski correlations to estimate the local heat transfer coefficient values. The experimental and predicted heat transfer coefficient values were used to determine an average convective heat transfer coefficient weighted by the heat transfer area. The results from this methodology were used in an analytically derived procedure for freezing-time estimates and then compared with experimental results. The average effective heat transfer coefficient underestimated freezing times and demonstrated a higher level of accuracy than the Gnielinski correlation when applied to boxes containing smaller product amounts. For experiments with greater quantity of products, the use of average heat transfer coefficients from the Gnielinski correlation yielded errors lower than 20%. Based on boundary layer theory, the Gnielinski correlation can be used to explain the isotherm behaviors observed during freezing. Many of the results satisfy the standards of accuracy used in engineering, and the procedure does not require extra computational effort. Springer Science+Business Media, LLC, 2011 Heat transfer coefficient nationallicence Freezing time nationallicence Gnielinski correlation nationallicence Fruit pulp nationallicence Temperature variation nationallicence de Resende Jaime Federal University of Lavras, Department of Food Science, Laboratory of Food Refrigeration, P.O. Box 3037, 37200-000, Lavras, MG, Brazil aut Prado Mônica Federal University of Lavras, Department of Food Science, Laboratory of Food Refrigeration, P.O. Box 3037, 37200-000, Lavras, MG, Brazil aut Junior Vivaldo State University of Campinas, Faculty of Food Engineering, P.O. Box 6121, 13083-970, Campinas, SP, Brazil aut Food and Bioprocess Technology Springer-Verlag 6/1(2013-01-01), 146-159 1935-5130 6:1<146 2013 6 11947 https://doi.org/10.1007/s11947-011-0757-6 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11947-011-0757-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- de Resende Jaime Federal University of Lavras, Department of Food Science, Laboratory of Food Refrigeration, P.O. Box 3037, 37200-000, Lavras, MG, Brazil aut NATIONALLICENCE 700 1- Prado Mônica Federal University of Lavras, Department of Food Science, Laboratory of Food Refrigeration, P.O. Box 3037, 37200-000, Lavras, MG, Brazil aut NATIONALLICENCE 700 1- Junior Vivaldo State University of Campinas, Faculty of Food Engineering, P.O. Box 6121, 13083-970, Campinas, SP, Brazil aut NATIONALLICENCE 773 0- Food and Bioprocess Technology Springer-Verlag 6/1(2013-01-01), 146-159 1935-5130 6:1<146 2013 6 11947 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer