Predicting Temperature Range in Food Slabs Undergoing Long Term/Low Power Microwave Heating

摘要

The contribution of standing wave patterns to nonuniform heating in homogeneous slabs was examined through the development of equations for various heating situations relating temperature distribution to thermal, geometric and dielectric properties. The equations were solutions to the differential heat equation, which incorporated a volumetric heat generation term based on a full solution to Maxwell's equations. This analysis was based on steady-state microwave heating resulting in either steady temperatures or temperature profiles and was thus applicable only to very long term heating and, where food is concerned, low power heating as well. This latter stipulation allowed the additional assumption of temperature-independent thermal and dielectric properties. Results were reported in the form of the minimum-to-maximum temperature range, indicating the degree of nonuniformity. Parameter values for agar gel and cooked beef were used to illustrate the behavior of the equations. For both types of food it was found that the temperature range was a very sensitive sinusoidal function of slab width. Furthermore, for slab widths of 10 cm or less, it was found that insulation at the slab faces significantly reduced the temperature range. Future work will determine if this approach can be extended to short term/high power applications.