Semiempirical Fouling Kinetics Model in Batch and Continuous Direct Ohmic Heating of Milk

Abstract

The direct ohmic heating has been one of modern heating technology at which an electrical current passing directly through an electrically conductive medium generates the heat. During milk ohmic heating fouling deposits can be formed due to milk protein degradation. The fouling removal requires periodical cleaning that increases costs of energy, detergents and wastewater treatment.Simple semiempirical generalized correlation quantifying the effect of concentration and temperature onto electrical conductivity was proposed and tested on published data of milk, coffee and aqueous H 2 TiF 6 solution. The semiempirical fouling kinetics model was proposed and verified in direct batch ohmic heating of milk. The model is based on the analogy to mechanisms and chemical kinetics of serial reactions. The effect of flowrate onto the fouling formation in continuous direct ohmic heating of milk was investigated. The proposed empirical fouling kinetics model is based on the assumption that the growth rate of the fouling layer thickness depends on time exponentially. It was found that fouling layer growth intensity was not decreased by the higher wall shear stress induced by the higher flowrate. However increasing wall shear stress enlarged the maximal time tnf in which the fouling layer growth is negligible.

Design of an ohmic reactor to study the kinetics of thermal reactions in liquid products

“…This type of linear behavior has been reported by numerous authors studying a variety of products under different experimental conditions (Ayadi et al, 2004;Castro et al, 2004;Goullieux et al, 1997;Icier and Ilicali, 2005;Legrand et al, 2007;Pongviratchai and Park, 2007;Sarang et al, 2007;Sulc and Novi, 2007;Zareifard et al, 2003). However, it remained difficult to find reference values for the electrical conductivity of milk or infant formula.…”