Industrial microwave dryer: An effective design to reduce non-uniform heating

Abstract

Drying systems are widely used in food processing industries. There exist serious complications in their design and operation since the target is to minimize cost and energy while to increase efficiency and quality. Novel methods have been introduced to comply with such demand among which microwave technology is highlighted in the last decade. It is applied in this research as an applied solution for conventional hot air methods. The uniform distribution of electromagnetic field in the microwave cavity is however equivocal in the literature which may result in low quality dried products. To monitor the electromagnetic field distribution, a simulation process using Finite Element Methods was conducted. Three geometries were selected as the microwave cavity. Analysis of variance for the indicator of heat non-uniformity index showed that cavity size has significant effect (P < 0.05) on the index. Additionally, the positioning of magnetron lamps within the cavity was simulated and analyzed. It was shown that in cube and cylinder type cavities, the positioning of the lamp has no significant effect on the electromagnetic field distribution. However, this is not true when more than one lamp is used in the cavities. Due to interactions of the waves emitting from the magnetrons, slight shifting in the position of lamps results in meaningful alterations of the index and require meticulous simulations before any construction. Experimental validation of simulated results proved that simulation can cover the pattern of temperature distribution with R2 of 0.96.