Mathematical modelling of vacuum ohmic evaporation process

Abstract

Ohmic evaporation is a complex process in which heat and mass transfers take in place simultaneously. In this study, finite difference-FD and finite volume-FV models simulating the changes of temperature and water removed from tomato juice during the vacuum ohmic evaporation process (VOEP) were developed. Models considering the heat and mass transfer equations were combined. Experimental effective electrical conductivity and specific heat capacity relations were taken into account. For heating period, final temperature was predicted with errors of 3.4 ± 1.3 °C and 0.7 ± 1.3 °C, while the evaporation time prediction errors were 1.3 ± 1.6 min and − 2.1 ± 1.6 min for FV and FD models, respectively. It was concluded the effect of mixing was not important on temperature distribution for such a high consistency tomato paste compared to the heat generation effect during the ohmic evaporation process. The developed models could be used to predict process time, temperature history, and volume fraction at any time during the ohmic evaporation process.