Utilizzo di tecnologie avanzate per applicazioni di 'high speed cooking'
| Autor: | Gambato, Francesco |
|---|---|
| Jazyk: | italština |
| Rok vydání: | 2015 |
| Předmět: |
solid-state devices
uniform heating superfici di risposta microwave riscaldamento a microonde microwave heating riscaldamento uniforme GaN cottura COMSOL HEMT response surface ottimizzazione metamodel particle swarm optimization ottimizzazione con sciami di particelle food ING-IND/31 Elettrotecnica optimization ottimizzazione particle swarm optimization PSO ottimizzazione con sciami di particelle response surface superfici di risposta uniform heating riscaldamento uniforme food safety food cibo cottura sicurezza alimentare microwave oven forni a microonde COMSOL metamodel metamodellazione microwave heating microwave riscaldamento a microonde microonde microwave solid-state devices dispositivi a microonde a stato solido HEMT GaN LDMOS PSO forni a microonde microonde LDMOS microwave oven food safety Settore ING-IND/31 - Elettrotecnica dispositivi a microonde a stato solido metamodellazione sicurezza alimentare cibo optimization |
| Popis: | The microwave (MW) technology has become crucial in "high speed cooking" equipment. This new generation of cooker is still being refined and still finding its place in today's kitchens, but it is clear that these new high speed ovens can cook a wide variety of products and cook them faster than anything previously on the market. In ordinary cooking, heat is applied to the outside of food and it gradually penetrates to the inside. In MW cooking, the heat is generated within the food. Thus, a shorter heating time and a higher efficiency are some of the benefits of this technology. MW cooking is rapid, but non-uniform. MW heating is non-uniform mainly because of the inherently uneven distribution of the electromagnetic (EM) field inside the oven cavity. As the energy penetrates a lossy material, it is absorbed and less of it remains to penetrate further. Thus, energy absorption is non-uniform. Moreover, the energy absorption process is strongly affected by shape, size, dielectric properties of materials, position of the workload, as well as by the cavity geometry and dimensions. MW heating systems must provide uniform heating to obtain high quality products and avoid the so-called hot spots and cold spots. Traditionally, the temperature uniformity is accomplished by moving parts within the applicator, using mode stirrers, employing turntable or a combination of these techniques. Unfortunately, these techniques are not applicable within all type of resonant cavities. Other techniques which do not involve moving parts are: the pulsing MW energy or the phase shifting for different sources of MW energy. The phase shift technique and its effects on the EM field distribution and heating of a workload is discussed in the Thesis. The study of MW power sources has increased popularity among researchers in the field of cooking systems. In the last few years the innovative high frequency power solid state devices has gained much attention in place of magnetron due to their higher performances. In particular, a more careful control of the cooking process, which guarantees a more uniform heating of the foodstuff, can be achieved by using the solid state devices. This result can be reached, for instance, by using a properly phase shift for different sources of MW energy and it is discussed in the Thesis. Another solution, that is examined, involves the use of slots in the waveguide wall, which radiate EM energy from the waveguide. Since a multi slotted waveguide can be considered as an antenna array, a proper design of the slotted waveguide antennas, which feed the launch box and the MW applicator, is proposed in order to attain a more uniform temperature distribution without the need of moving parts. The effectiveness of the aforementioned technical solutions has been verified by means of numerical simulations on a test case model of practical interest, named "panini grill". The use of MW technology ensures a sandwich is heated through without a cold centre while reducing cooking time significantly. In the 3D numerical model two physical phenomena, i.e. EM wave propagation and heat transport, are coupled together by the thermal effects of MW energy deposition and the temperature-dependent material parameters. The coupled problem is solved by means of a FEA commercial software (COMSOL). In order to achieve the design parameters for the slotted waveguide feeding system and the phase shifting, which guarantee the more uniform hating, an optimization problem has been solved. More specifically, a metamodels-based optimization method has been set up. The metamodels can significantly reduce the problem complexity and simulation time. The optimization procedure has been characterized by pre-processing, programming, and post-processing coupling COMSOL Multiphysics and Matlab software. |
| Databáze: | OpenAIRE |
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