Using the computational fluid dynamics to analyze the thermal sterilization of solid–liquid food mixture in cans

Abstract

Flow pattern, temperature distribution and shapes of the slowest heating zone during heating of solid–liquid food mixture (pineapple slices saturated with its moisture) in a cylindrical can of 84 mm diameter and 82 mm height are predicted. The partial differential equations describing the conservation of mass, momentum and energy are solved numerically using commercial computational fluid dynamics (CFD) software (PHOENICS), which is based on a finite volume method of analysis. Saturated steam at 121 °C is used as a heating medium, where the metal can is heated from all sides. The model liquid is assumed to have constant properties except for the viscosity (temperature dependent) and density (Boussinesq approximation). Two methods of analysis are adopted in the simulation. In one of the methods, the pineapple slices are assumed permeable to natural convection flow in its pores, while in the second method, the pineapple slices are assumed impermeable. The results of the simulations of both cases are very similar. The simulations show, the action of natural convection on the rate of heating, liquid flow pattern and on the shape and movement of the slowest heating zone (SHZ). The SHZ eventually stays in a region that is about 30–35% of the can height from the bottom. Industrial relevance The authors indentified the interesting and obviousely so far neglected topic of natural convection during sterilization heating of solid-liquid food mixtures in containers. The by simulation results obtained suggest that the configuration of the solid in the container can significantly influence the rate of heating. This may also be of significance for other processes such as high hydrostatic pressure treatment or ohmic heating.