Microwave heating is extremely popular as a household method for warming up foodstuffs quickly. However the industrial application of this convenient, pollution free heating technique is very limited because of its non-uniform temperature distribution with hot and cold spots. The temperature distribution in microwave heating depends on the electromagnetic frequency, processing time, size and shape, and dielectric properties of the object being heated. In this paper, we present a close form analytic solution for temperature distribution in a three dimensional rectangular block under microwave processing. With the knowledge of electric field distribution from Maxwell's equation, a three dimensional, unsteady, non-homogenous energy equation containing a microwave source term is solved by the integral transform technique. The effects of various parameters such as sample thickness, electromagnetic frequencies, dielectric properties, and processing time are studied for a salmon fillet. The results indicate that the proper integration of incident frequencies, dielectric properties, sample thickness and processing time could provide homogenous temperature distribution in a salmon fillet under microwave heating.
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