Methods for evaluating the effect of large voids on food package cooling times

摘要

Design of food package cooling operations requires accurate prediction of chilling or freezing time, temperature-time profile and heat release rate. Current algebraic and ordinary differential equation prediction methods assume an homogenous product and account for the effects of air voids through the use of effective thermal properties. Many packaged foods, however, contain voids large enough to allow natural convection to develop, or gaps that change the directions and lengths of heat conduction pathways. The effect of these phenomena may be significant enough to render current prediction methods unsuitable. The initial step in developing a simple method to predict the cooling times of these packages is to measure the effects of large voids on temperature-time profiles in the packages. In this paper, an experimental methodology for evaluating the effects of large voids was developed. The accuracy of the method is investigated and compared to numerically simulated results. Preliminary conclusions about the effect of various void sizes are made.