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A finite element model for conduction errors in thermocouples during thermal sterilization of conduction‐heating foods
Author(s) -
KANELLOPOULOS G.,
POVEY M. J. W.
Publication year - 1991
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.1991.tb01984.x
Subject(s) - thermal conduction , thermocouple , thermal diffusivity , materials science , penetration (warfare) , heat transfer , thermal contact , finite element method , mechanics , sterilization (economics) , thermal conductivity , thermodynamics , composite material , mathematics , physics , operations research , monetary economics , economics , foreign exchange market , foreign exchange
Summary Errors in temperature measurement due to heat conduction along thermocouples employed in heat penetration studies of food which is heated by conduction have been quantified, using a finite element numerical solution of the unsteady state heat transfer equation. For a 0.56‐mm (24s.w.g.) Type T thermocouple, temperature at the centre of a can may be overestimated by over 2°C in the heating phase of a typical process. The errors are much larger for thicker thermocouples. The orthodox conservative design strategy for thermal processes, relying on the lethal effect of the heating phase and treating the cooling phase as a safety margin, may not be a ‘safe’ strategy. The conduction errors result in an overestimate of the heating‐phase lethality and an underestimate of the cooling‐phase lethality. The application of a correction to the lag factor is not adequate to compensate for the derestimation of the lethality during the cooling stage. The errors in the determination of the thermal diffusivity from heat‐penetration data are much lower than the errors in the determination of the sterilization effect delivered by a particular process. The silicon elastomer used to experimentally validate the model employed in this study, is shown to be an ideal material to model food which is heated by conduction.