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DETERMINING CONVECTIVE HEAT TRANSFER COEFFICIENT (h) FOR HEATING AND COOLING OF BOTTLES IN WATER IMMERSION
Author(s) -
AUGUSTO PEDRO E.D.,
PINHEIRO TALITA FERRAMOLA,
CRISTIANINI MARCELO
Publication year - 2012
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/j.1745-4530.2009.00571.x
Subject(s) - biot number , heat transfer coefficient , convection , convective heat transfer , thermodynamics , heat transfer , materials science , heat flux , mechanics , process engineering , physics , engineering
Thermal process, specially the in‐package process, is one of the safest and most frequently used methods for food preservation. Mathematical models for heat transfer have been widely used as a powerful tool in safety and high‐quality food process design. The convective heat transfer coefficient (h) is essential for heat flux calculation in model boundary conditions, and its determination must be done by the actual heat transfer system. The present study has determined the h‐values for two commercial bottles (G1 and G2) in two water immersion systems, one for heating and one for cooling. It was calculated by an inverse heat transfer problem, using computational fluid dynamics. Two methodologies for h determination were compared, using either a conductive material or a convective material inside the packages. The methodology that uses a conductive material showed simpler and faster computational simulation, but presented a limitation related with the Biot number of the process. Results indicated a limitation in the most used methodology for h determination, and suggest that the convective material methodology can be an alternative for this analysis. For the same systems, the h heating value for G1 was almost 50% higher than for G2, and h cooling values for G1 were almost 70% higher than for G2. Differences obtained between bottles highlight the need to determine h for the exact heat transfer system. Moreover, these results indicate that there is a potential for process optimization only by varying its package format, as it can influence the heat flux for the packaging.PRACTICAL APPLICATIONS The results obtained from this study highlight the influence of geometry on the convective heat transfer coefficient among bottles and immersion water systems. It also confirms the possibility of optimizing the thermal process through package format changes, allowing the obtainment of safer products with better sensorial and nutritional characteristics at a lower cost and energy expenditure. However, further studies are needed to better understand the package geometry in thermal processes. On the other hand, it contributes for thermal processes studies as it stands out the importance of determining this property for the actual system studied, besides showing its limitations for determination based on a conductive product widely utilized in the literature.