State of the art of the fundamental aspects in the concept of microwave-assisted heating systems

Abstract

As the processing of materials using clean energy becomes increasingly important, indirect conventional heating

is being replaced by microwave-assisted heating. This method transforms energy directly into heat, providing

rapid heating with instantaneous start-up, improved control and homogeneity of temperature distribution, and

enabling a compact design. Therefore, the impact of microwaves in industry is growing in recent years. The

complexity of incorporating microwaves into any industrial process resides in the need for a customised design.

This is emphasised in the case of continuous flow microwave heating systems where the electromagnetic distribution

and its transformation into heat, as well as the dynamics of the fluid to be heated under different

operating conditions, are solved. For this purpose, and apart from the dielectric and magnetic properties of the

material to be heated, which define how it behaves in relation to electric and magnetic fields when exposed to

microwaves, there are several factors influencing the design of the process: the microwave generator and the

transmission line, the geometry of the applicator where the electromagnetic field is distributed, the material

container of the sample or the temperature measurement techniques to control the process. Additionally, numerical

simulation is an essential tool for designing and predicting the suitability of any microwave system. This

is the case of composite materials processing, where the application of numerical simulation tools arises from the

need to achieve advanced materials more efficiently. In this paper, these fundamental aspects for the design of a

microwave-assisted heating system are reviewed, presenting examples of various applications where this microwave

technology is integrated.