DEVELOPING AN EFFECTIVE METHOD TO DETERMINE THE DEVIATION OF F VALUE UPON THE LOCATION OF A STILL CAN DURING CONVECTION HEATING USING CFD AND SUBZONES

초록

A numerical simulation was applied to determine the temperature profiles of water in a can with a diameter of 52.3mm and a height of 124.0mm. Cold points at different heating times were determined, and the degree of pasteurization (F value) of each cold point was calculated. Subzones in both vertical and horizontal directions were introduced to determine the deviation of F value upon the location in the can during a convective heating, and the average F value of each subzone was estimated. The slow heating zone (SHZ) was determined by overwrapping the subzones with the lowest average F values in the vertical and horizontal direction. The cold point was continuously moved during the thermal treatment and even at 600s, the SHZ determined by this subzone method maintained a single zone, unlike the cold points. The relative difference of F value between the SHZ and the cold point was approximately 0.575%. The subzone method is thus an effective way to determine the SHZ and F value, which is an indicator of the sterilization. Practical ApplicationsFor safety purposes, estimation of the degree of pasteurization is very important for the liquid food in a can. Determination of the slow heating zone (SHZ) and F value in the can is very difficult because of the convection flow during heating. Many previous studies indicated the importance of determining the SHZ for the liquid food in a can, but there was no clear advice to estimate the degree of pasteurization based on the temperature profile from the SHZ. This study suggested to use the subzones to estimate the SHZ and clearly demonstrate that the degree of pasteurization at the SHZ represented by the area average F value obtained from the subzone is more stable and consistent.

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