An improved method to estimate temperatures and lethality during the cooling stage of sterilized cylindrical cans.

摘要

The apparent position numerical solution (APNS) method, which is based on the solution of the heat transfer equation for a spherical geometry, is commonly used in thermal treatment calculations to accurately predict the temp. history of products in containers of arbitrary shapes. This is accomplished by finding the 'apparent position' within a sphere that represents the actual temp. profile at the slowest heating and cooling points of a canned food container of arbitrary geometry. The APNS method provides a good temp. prediction during the late heating sterilization stage of processes that have approx. constant heating temp. or those that have heating temp. experiencing small deviations. However, the agreement between the temp. predicted by the APNS method and the actual temp. of the product at a given location is not good in the initial stage of the process cooling phase. An equation to calculate differences between the temp. at any location of a cylindrical container and that predicted by the APNS method was derived from the heat transfer equations governing the thermal process. By incorporating the calculated temp. differences into the APNS method, during the cooling phase, a better agreement between the actual and predicted temp. was obtained for several process conditions.