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Theses

Traitement thermique des fluides alimentaires encrassants par la technologie du chauffage ohmique en géométrie rectangulaire

Abstract : An experimental study on the heat treatment of fouling food fluid by flat ohmic cells was carried out. This study highlighted first of all the close link existing between the flow structure and the deposit distribution on to electrode surfaces. Measurements of velocity and temperature profiles in a non-fouled ohmic cell showed that according to the hydrodynamic behavior (velocity profile and rheologic behavior of the fluid) the variation in the temperature gradient between the wall and the bulk could be more or less significant. Then, a specific study of the heat treatment of a fouling model fluid in an ohmic cell was carried out. This study showed the existence of three distinct phases: (i) a first phase in which no evolution of the process parameters could be observed, (ii) a linear phase, where the deposit layers build up on the electrode surfaces was heated continuously by the Joule effect until reaching the boiling point and (iii) a third phase which corresponded to an overheating of the deposit layers with potential removal phenomenon. Lastly, based on the results obtained, a mathematical model was developed in order to predict the thickness of the deposit from the evolution of the electric parameters versus the operating time. The comparison between a Plate Heat Exchanger and the ohmic apparatus in terms of deposit thickness clearly showed different kineticks evolutions, apparently in favour of the ohmic technology.
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http://docnum.univ-lorraine.fr/prive/SCD_T_2005_0002_AYADI.pdf
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Submitted on : Thursday, March 29, 2018 - 10:40:02 AM
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Mohamed Ali Ayadi. Traitement thermique des fluides alimentaires encrassants par la technologie du chauffage ohmique en géométrie rectangulaire. Autre. Université Henri Poincaré - Nancy 1, 2005. Français. ⟨NNT : 2005NAN10002⟩. ⟨tel-01746545⟩

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