Heat Treatment of Whole Milk by the Direct Joule Effect—Experimentaland Numerical Approaches to Fouling Mechanisms

Autor: Fillaudeau, L., Winterton, Peter, Leuliet, J. C., Tissier, J. P., Maury, V., Semet, F., DEBREYNE, P., Berthou, M., Chopard, F.
Přispěvatelé: Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés (LISBP), Institut National de la Recherche Agronomique (INRA)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Génie des Procédés et Technologie Alimentaires (LGPTA), Institut National de la Recherche Agronomique (INRA), Technologies et Recherche pour l'Efficacité Energétique (EDF R&D TREE), EDF R&D (EDF R&D), EDF (EDF)-EDF (EDF), Alfa Laval Vicarb
Jazyk: angličtina
Rok vydání: 2006
Předmět:
Zdroj: Journal of Dairy Science
Journal of Dairy Science, American Dairy Science Association, 2006, pp.4475-4489
ISSN: 0022-0302
Popis: International audience; The development of alternative technologies such as the direct Joule effect to pasteurize and sterilize food products is of great scientific and industrial interest. Our objective was 1) to gain insight into the ability to ensure ultra-high-temperature treatment of milk and 2) to investigate the links among thermal, hydraulic, and electrical phenomena in relation to fouling in adirect Joule effect heater. The ohmic heater [OH;→→E⊥v (where E is the electrical field and v is the velocity); P (power) = 15 kW] was composed of 5 flat rectangular cells [e (space between the plate and electrode) = 15 mm, w (wall) = 76 mm, and L (length of the plate in plate heat exchanger or electrode) = 246 mm]—3 active cells to ensure heating and 2 (at the extremities) for electrical insulation and the recovery of leakage cur- rents. In the first step, the thermal performance of the OH was investigated vs. the flow regimen [50 < Re (Reynolds number) < 5,000], supplied power (0 < P < 15 kW), and electrical conductivity of fluids (0.1 < σ20°C < 2 S/m) under clean conditions with model fluids. This protocol enabled a global thermal approach (thermal and electrical balance, modeling of the temperature pro- file of a fluid) and local analysis of the wall temperature of the electrode. An empirical correlation was estab- lished to estimate the temperature gradient, Tw − Tb (where Tw is the wall temperature and Tb is the product temperature) under clean conditions (without fouling) and was used to define operating conditions for pure- volume and direct-resistance heating. In the second step, the ability of OH to ensure the ultra-high-temper- ature treatment of whole milk was investigated and compared with a plate heat exchanger. Special care was taken to investigate the heat transfer phenomena occurring over a range of temperatures from 105 to 138°C. This temperature range corresponds to the part of the process made critical by protein and mineral fouling. The objectives were 1) to demonstrate the abil- ity of an OH to ensure heat treatment of milk, 2) to study the thermal and hydraulic performance with an increasing power and temperature difference between the inlet and outlet of the OH, 3) to define and validate a criterion to follow heat dissipation efficiency, and 4) to compare the fouling propensity with the different configurations. A heat dissipation coefficient, RhCO, was defined and validated to monitor the fouling propensity through global electrical and thermal parameters. Fi- nally, a numerical simulation was developed to analyze heat profiles (wall, deposit, bulk). Because of an increas- ing Joule effect in the static deposit, the simulation showed how wall overheating would definitively cause fouling to spiral out of control.Key words: ohmic heating, wall overheating, fouling, whole milk
Databáze: OpenAIRE
Externí odkaz: