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Experimental characterization and modelling of the evaporation phenomena on surfaces of a cold room.

Caractérisation expérimentale et modélisation des phénomènes d'évaporation sur les parois d'une enceinte réfrigérée.

Author(s) : LECOQ L.

Type of monograph: Doctoral thesis

Summary

The aim of this Ph.D. thesis is to develop a methodology to predict drying rate on walls in a food processing plant. This methodology is based on studies at different scales to analyze the heat and mass (water) exchanges in a food plant. Three laboratory studies were performed: a ventilated box (~0.001 m 3), a wind tunnel (~0.02 m3), a cold room (~30 m3) and one in a food processing plant (~450 m 3). Numerical (Comsol) and analytical models were developed to predict water evaporation rate on a solid surface (stainless steel, PVC) and validated with experimental data obtained in the wind tunnel and the cold room. For the experimental conditions studied, the results shown that relative humidity was the most influential factor on the evaporation rate. A simplified heat and mass transfer model was developed to predict the water mass evolution on the walls of a food plant in function of ambient conditions. This model is based on a zonal approach that considers three walls: wall, floor and equipment. The influence of a dehumidifier was studied. The experimental and numerical results showed that the dehumidifier allowed the reduction of relative humidity in the room from 90% to 60% which reduced the drying time by about 1.5 times. It was shown that the equipment dries the slowest due to its low thermal inertia, consequently, water was still remained after 2h (drying duration in the food plant). In order to increase the evaporation rate on the equipment, it was estimated by the model that 50 W.m-2 of heat supply could be provided to complete drying. Finally, this model was coupled to predictive microbiology model where the parameters were identified using the experimental data of the Listeria monocytogenes cultivability exposed to different relative humidity in the ventilated box (UMR PAM and ANSES collaboration). The results showed that the inactivation was the highest at 68% of relative humidity and that with the heat supplied to equipment of 50 W.m-2, the minimal of bacterial load would be reached after 5 hours instead of 12 hours without heat supply.

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Pages: 229 p.

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Details

  • Original title: Caractérisation expérimentale et modélisation des phénomènes d'évaporation sur les parois d'une enceinte réfrigérée.
  • Record ID : 30032279
  • Languages: French
  • Subject: Technology
  • Publication: AgroParisTech - Antony - France
  • Edition statement: Institut agronomique, vétérinaire et forestier de France
  • Publication date: 2016/10/06

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