Editor’s message: computer modeling for design of microwave systems

Editor's message: computer modeling for design of microwave systemsOne of the mandatory thermodynamic and kinetic conditions that must be complied with for conducting chemical and physical processes is the temperature.Therefore, research aimed at enhancing such processes deals with the effectiveness of heating and its control.The design of devices and techniques for conducting microwave processes requires a strong knowledge of the involved phenomena and their interaction over the thermal response of the system.The set of equations that must be solved is huge, so that computer aid is necessary to have results in practical times.The models, proposed by scientists in physics, chemistry and mathematics, are cast in the form of algorithms in computers that perform the operations and provide results in an understandable way, that is with plots, color charts and virtual prototypes that can be tested, providing evaluable data useful for feedback to adjust a design or to define the most suitable processing conditions.The use of computers in this way is an important element in computer modeling.Computer power itself is not of assistance in the design of systems if the models do not include the scientific background of this technology dealing with aspects ranging from empirical knowledge to the most sophisticated theoretical advances.Here are some of these aspects.Empirical relationships regarding heating have been learned from the experience using and controlling fire, not only in its early use for cooking, but in ancient technologies, ceramic, glass, and metallurgy.Then, it is not rare that there are simplified rules of heating; for example, proposing that a sample heated in an oven one hour per inch thickness is enough to achieve a uniform temperature.This rule found in heat treatments of steels might have a sort of analogy for meals in a time cooking chart.This general practical guidance might apply in ordinary situations that tolerate some deviations but it cannot be extrapolated without considering Fourier's equation.The uncertainty of the rule leads to complementary adjustments to be safe, so that the samples might be overexposed.There is no concern regarding overheating since in conventional heating that does not occur as for microwaves, however extra time is against energy efficiency and productivity, not to mention changes in the sample, like overcooking.Knowledge of temperature evolution in a system is essential for the design of devices and procedures; in some cases, practical measurements can be taken, while in others, especially in designing, are made by applying models based on heat transfer theory.There are several classical solutions that can be found even in coursebooks, showing cases for slabs, cylinders, and spheres, with a variety of boundary conditions that lead to present temperature as function of the thermal diffusivity, position, and time.