The effect of can rotation on sterilization of liquid food using computational fluid dynamics

摘要

In this work, sterilization of a viscous liquid food (carrot-orange soup) in a metal can lying horizontally and rotated axially in a still retort was simulated. The rotating can at 10 rpm was assumed to be heated by steam at 121℃. The governing equations of mass, momentum and energy conservation for the three-dimensional can were solved using a commercial computational fluid dynamics package (PHOENICS), which is based on a finite volume method of solution. Transient temperature and velocity profiles caused by natural and forced convection heating were presented and compared with those for a stationary can. The results indicated that the combined effect of natural and forced convection splits the slowest heating zone (SHZ) into two distinct regions, unlike what has been previously observed in the stationary can. The volume of the SHZ was found to cover less than 5% of the total volume of the rotated can at the end of heating, which is due to the effect of rotation. The magnitude of the maximum axial velocity of the fluid after 1000 s of heating was found ranging from 2.3 x 10~(-5) to 3.2 x 10~(-4) ms~(-1), compared with 2.2 x 10~(-7) to 2.1 x 10~(-4) ms~(-1) for the stationary can. The localized high velocity near the two ends of the can spread gradually throughout the whole length of the can as heating progresses.