Modeling Of Microwave Heating Research Articles

Enhanced Computer Modelling for High Temperature Microwave Processing of Ceramic Materials

AbstractA new software package is described for 2-Dimensional modelling of microwave heating. It is particularly suited to the high temperature heating of ceramics, where electrical and thermal properties are strongly dependent on temperature. The described program, x_tlm, runs under Xwindows, which allows a microwave cavity and its contents to be entered graphically and stored as a schematic diagram. The diagram is automatically converted into a mesh format for simulation using a topology independent Transmission Line Modelling formulation. Temperature dependencies of material properties are specified as polynomial functions of temperature. Surface heat loss by the radiation mechanism, which dominates at higher temperatures, is also introduced into the model.

Tray-shape effect in a computational model of microwave heating

Tray-shape effect in a computational model of microwave heating

An Original Way to Select and Control Hydrodynamic Instabilities: Microwave Heating.: Part IV: Energy considerations and electric field effects.

The purpose of this work is the comparison between hydrodynamic behaviors observed during water and ethanol evaporation induced by microwave heating and simultaneously under reduced pressure, in order to generalize the specificity of the microwave heating in relation to thermal dependency. Modeling of microwave heating for the case of a liquid column is described. Thermal dependency of the electric field is taken into account. This model owing to fluid properties makes it possible to obtain changes of the thermal spatial profile. Numerical data, according to experimental results, proves that for liquids as water with dielectric loss decreasing with temperature, thermal conversion of the electromagnetic energy is preponderant in cold areas. For liquids as ethanol with dielectric loss increasing with temperature, thermal conversion of the electromagnetic energy is preponderant in hot areas. Thus, hydrodynamic instabilities selection results from the thermal dependency of the dielectric loss. Conclusions about superheating, boiling, and explosion occurring in microwave heating of liquids are given.

Some similarity temperature profiles for the microwave heating of a half-space

AbstractThere is presently considerable interest in the utilisation of microwave heating in areas such as cooking, sterilising, melting, smelting, sintering and drying. In general, such problems involve Maxwell's equations coupled with the heat equation, for which all thermal, electrical and magnetic properties of the material are nonlinear. The heat source arising from microwaves is proportional to the square of the modulus of the electric field intensity, and is known to increase with increasing temperature. In an attempt to find a simple model of microwave heating, we examine here simple transient temperature profiles corresponding to a heat source with spatial exponential decay but increasing with temperature, for which we assume either a power-law dependence or an exponential dependence. The spatial exponential decay is known to apply exactly when the electrical and magnetic properties of the material are assumed constant. A number of transient temperature profiles for this model are examined which arise from the invariance of the governing heat equation under simple one-parameter transformation groups. Some closed analytical expressions are obtained, but in general the resulting ordinary differential equations need to be solved numerically, and extensive numerical results are presented. For both models, these results indicate the appearance of moving fronts.

A Mathematical Model for Microwave-Assisted Chemical Vapor Infiltration

ABSTRACTA model for microwave heating of a ceramic preform is presented. Microwave power and external cooling are manipulated to obtain desired temperature profiles for effective chemical vapor infiltration (CVI) of the preform. A mass transport and chemical reaction model is developed to demonstrate preform densification. Conditions affecting matrix deposition are evaluated.

MATHEMATICAL MODELING OF MICROWAVE HEATING BY THE METHOD OF DIMENSIONAL ANALYSIS

Dimensional analysis was used to develop a predictive mathematical model for microwave heating of water. Water properties (density, specific heat, thermal conductivity and dielectric loss factor), power output and frequency of microwave, and geometric parameters were included in the dimensionless terms. Two household microwave cavities (donated by Tappan and Litton) were used. Time-temperature data were collected using a Luxtron fluoroptic temperature sensor (model 750) equipped with fiber optic probes. the predictive model, which was based on data taken in a Litton microwave cavity, was used to predict heating time of water in a Tappan microwave cavity. the results showed good agreement between the measured and the predicted time duration, with a high correlation coefficient (R2=. 99).

A simple power deposition model for microwave heating in EBT-I

A simple model is presented for the production and absorption of ordinary- and extraordinary-mode energy in various regions of the ELMO Bumpy Torus plasma. The plasma is divided into two regions: (I) the low-magnetic-field side of the extraordinary-mode cutoff and (II) the high-field side of the cut-off. Energy balance equations are written for the sources (injection, mode conversion, and tunnelling) and sinks (mode conversion, absorption, and tunnelling) in each region, and simplified models are introduced to account for each of these processes. Since a typical ray makes several reflections from cavity wall surfaces before being absorbed, additional simplifying assumptions are made that the wave fields are an isotropic incoherent superposition of plane waves and that the energy density of each mode is uniform in a given region. – It is found that conversion between eigenmodes upon wall reflection and absorption of the extraordinary mode at the fundamental cyclotron resonance are the most rapid processes in EBT-I. The relative fractions of the injected power deposited in the various plasma components are typically 25% to the annulus, 22% to the core plasma, and 53% to the surface plasma. The partitioning of energy between the three plasma components is determined largely by geometric characteristics of the walls, the plasma, and the fundamental cyclotron resonant surface. The results are comparatively insensitive to other parameters of the model and in rough agreement with estimates of power deposition based on experimental data.

Microwave heating of the ELMO Bumpy Torus relativistic electron ring

A model for microwave heating of electron rings in the ELMO Bumpy Torus configuration is analyzed using a relativistically correct quasi-linear formulation. The spatial locations of heating by the different electron-cyclotron harmonics are calculated. The steady-state ring energy and the microwave power required to sustain the rings are determined by balancing the line-averaged heating rate against classical collisional and radiative energy loss processes. Although ring formation is generally attributed to the second harmonic electron-cyclotron resonance, the calculations show that fundamental heating also plays a critical role in ring start-up and steady state. The model predicts ring power requirements for EBT which are consistent with previous estimates.