Modeling microwave heating in blocks, cylinders and spheres

This is a post-print. The definitive version can be found in Proceedings 2006 ASABE Annual International Meeting, pages pp. 1-11, Portland, Oregon, USA.The factors, which determine the temperature in microwave-heated food, include the applied power, exposure time, the geometry of the microwave applicator, the geometry and size of the heated food and the electromagnetic and thermal properties of the food. Uneven temperature distribution within microwave-heated food is commonly reported. Coupled with this, any realistic analysis of microwave heating in moist food must account for simultaneous heat and moisture diffusion through the material. Analysis of simultaneous heat and moisture diffusion predicts that two waves of heat and moisture diffusion will result from microwave heating. It appears that the faster of these two diffusion waves is the dominant factor during microwave heating. This paper presents a summarised derivation of solutions to the forced diffusion equations that describe simultaneous heat and moisture transport during microwave heating of rectangular blocks, cylinders and spheres. These equations describe the subsurface heating in rectangular block and the core heating in small radii cylinders and spheres. They also predict the transition to surface heating in cylinders and spheres as their radii increase or the microwave attenuation factor of the food becomes larger.9 - 12 July 200