Modeling of Heat Transfer Characteristics in Stir-frying Processes

Abstract

Though many kinds of machineries are needed for the automated food processing, the designing method for food machineries is not well developed. This is due to the complexity of the heat transfer characteristics in foodstuff, and the stir-frying process is the most complicated one that includes simultaneous heat and material transfer. In this article, heat transfer mechanism in stir-frying process is studied in detail. Temperature distribution in static bulk of sprouts is measured and the obtained data reveal the fact that the temperature hardly rise in the pieces that do not touch the heating surface. This fact notice us the stirring operation has an extremely important roll even in heat transfer since it substitute the thermal diffusion by its material dispersion. On the basis of these disclosures, thermal characteristics of a static bulk is estimated by introducing 2 parameters; one-layer thickness and fraction of contacting pieces. In addition, thermal diffusion due to stirring operation is modeled by introducing the parameter named stirring frequency. These enabled to establish the calculation method that can predict the temperature rise in stir-fried bulk. From one of calculation results, heat transfer coefficient between bulk and heating surface is estimated as 155 W/m²K.