Theoretical Analysis of Microwave Heating of Dielectric Materials Filled in a Rectangular Waveguide With Various Resonator Distances

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Phadungsak Rattanadecho ◽  
Waraporn Klinbun
Keyword(s):  
Microwave Heating ◽  
Rectangular Waveguide ◽  
Control Volume ◽  
Saturated Porous Medium ◽  
Simple Algorithm ◽  
Dielectric Materials ◽  
Microwave Cavity ◽  
Heating Process ◽  
Finite Control ◽  
Volume Method

This paper proposes mathematical models of the microwave heating process of dielectric materials filled in a rectangular waveguide with a resonator. A microwave system supplies a monochromatic wave in a fundamental mode (TE10 mode). A convection exchange at the upper surface of the sample is considered. The effects of resonator distance and operating frequency on distributions of electromagnetic fields inside the waveguide, temperature profile, and flow pattern within the sample are investigated. The finite-difference time-domain method is used to determine the electromagnetic field distribution in a microwave cavity by solving the transient Maxwell equations. The finite control volume method based on the SIMPLE algorithm is used to predict the heat transfer and fluid flow model. Two dielectric materials, saturated porous medium and water, are chosen to display microwave heating phenomena. The simulation results agree well with the experimental data. Based on the results obtained, the inserted resonator has a strong effect on the uniformity of temperature distributions, depending on the penetration depth of microwave. The optimum distances of the resonator depend greatly on the operating frequencies.

scholarly journals Microwave-induced heating behavior of Y-TZP ceramics under multiphysics system

2020 ◽  
Vol 9 (1) ◽  
pp. 119-130
Author(s):  
Kaihui Cui ◽  
Tianqi Liao ◽  
Chen Qiu ◽  
Hua Chen ◽  
Junwen Zhou
Keyword(s):  
Numerical Model ◽  
Microwave Heating ◽  
Three Dimensional ◽  
Heating System ◽  
Dielectric Materials ◽  
Microwave Cavity ◽  
Heating Process ◽  
Highly Sensitive ◽  
Dimensional Distribution ◽  
Heating Behavior

AbstractThis paper aims to investigate the heating behaviors of Y-TZP arrays under microwave irradiation. In this study, a three-dimensional numerical model of the microwave heating system was developed by COMSOL Multiphysics software. The numerical model was verified by microwave heating experiment, and the average root means square errors (RMSE) between the simulation and experimental data also confirmed the reliability of the model. The varying position and arrays of materials were applied to predict and visualize the three-dimensional distribution of the electromagnetic field and temperature during the microwave heating process. The results show that the temperature field distribution in microwave cavity was highly sensitive to the dielectric materials, the arrangement of the Y-TZP array interfered with the distribution of standing waves. The results can serve as references for the study to design and optimize the ceramic’s application in terms of microwave heating.

Natural Convection in a Saturated Variable-Porosity Medium Due to Microwave Heating

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Watit Pakdee ◽  
Phadungsak Rattanadecho
Keyword(s):  
Porous Medium ◽  
Microwave Heating ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Saturated Porous Medium ◽  
Simple Algorithm ◽  
Heating Process ◽  
Variable Porosity ◽  
Dimensional Variation ◽  
Difference Time

Microwave heating of a porous medium with a nonuniform porosity is numerically investigated based on a proposed numerical model. A two-dimensional variation of porosity of the medium is considered. The generalized non-Darcian model developed takes into account the presence of a solid drag and the inertial effect. The transient Maxwell’s equations are solved by using the finite difference time domain method to describe the electromagnetic field in the waveguide and medium. The temperature profile and velocity field within a medium are determined by solution of the momentum, energy, and Maxwell’s equations. The coupled nonlinear set of these equations is solved using the SIMPLE algorithm. In this work, a detailed parametric study is conducted on heat transport inside a rectangular enclosure filled with a saturated porous medium of constant or variable porosity. The numerical results agree well with the experimental data. Variations in porosity significantly affect the microwave heating process as well as the convective flow pattern driven by microwave energy.

A Thermo-Mechanical Model for a Counterflow Biomass Gasifier

2014 ◽  
Vol 354 ◽  
pp. 227-235
Author(s):  
Marcelo J.S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Control Volume ◽  
Simple Algorithm ◽  
Thermal Capacity ◽  
Macroscopic Model ◽  
Algebraic Equations ◽  
Medium Permeability ◽  
Mechanical Approach ◽  
Volume Method

This article presents a thermo-mechanical approach to investigate heat transfer between solid and fluid phases in a model gasifier. A two-temperature equation approach is applied in addition to a macroscopic model for laminar flow through a porous moving bed. Transport equations are discretized using the control-volume method and the system of algebraic equations is relaxed via the SIMPLE algorithm. The effects on inter-phase heat transfer due to variation of medium permeability, thermal conductivity and thermal capacity are analyzed. Results indicate that for smaller medium permeabilities, as well as for higher solid-to-fluid thermal capacity and thermal conductivity ratios, enhancement of heat transfer between phases is observed.

Numerical Simulation of Fluid Flow and Heat Transfer in the Micro-Nozzle

2005 ◽  
Author(s):  
Longjian Li ◽  
Yihua Zhang ◽  
Wenzhi Cui ◽  
Tien-Chien Jen ◽  
Qinghua Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Control Volume ◽  
Slip Model ◽  
Control Volume Method ◽  
Propulsion Performance ◽  
Micro Nozzle ◽  
Flow And Heat Transfer ◽  
Finite Control ◽  
Mems Technology ◽  
Volume Method

Micro-nozzle, based on the MEMS technology, has played an important role in orbit positioning, attitude adjusting and other applications of micro-satellites. The continuous no-slip model of two-dimensional compressible laminar flow in the micro-nozzle was proposed and solved numerically by finite control volume method. The flow and heat transfer in the micro-nozzle were computed under different conditions, including different inlet pressures, different inlet temperatures and different divergent angles. Flow field and effects of these conditions on the propulsion performance were analyzed. Finally, simulated solutions were compared and validated with the experimental results.

Numerical Simulation of Laminar Confined Impinging Jet in a Composite Channel

2008 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Porous Layer ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Local Distribution ◽  
Governing Equations ◽  
Stagnation Region ◽  
Volume Method ◽  
Material Porosity ◽  
Macroscopic Equations

This work shows numerical results for a jet impinging onto a flat plane covered with a layer of a porous material. Porosity of the porous layer is varied in order to analyze its effect on the local distribution of Nu. Macroscopic equations for mass and momentum ae obtained based on the volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Results indicate that inclusion of a porous layer decreases the peak in Nu avoiding excessive heating or cooling near the stagnation region.

Free convective of a linear heterogeneous liquid in a square cavity at side heating

2020 ◽  
pp. 108-116
Author(s):  
K.V. Moiseev ◽  
◽  
V.S. Kuleshov ◽  
R.N. Bakhtizin ◽  
◽  
...  
Keyword(s):  
Control Volume ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Double Diffusion ◽  
Boussinesq Approximation ◽  
Square Cavity ◽  
Cell Height ◽  
Volume Method ◽  
Dimensional Statement ◽  
Stratified Liquid

In this work the problem of free convection of the Newtonian poorly stratified liquid in the cell warmed up from left and cooled from right with the heat-insulated horizontal boarders is presented. Liquid with small concentration of salt and initial linear stratification on cell height is considered. The model of double diffusion in a Boussinesq approximation is applied to model the process. The problem is solved both in two - and three-dimensional statement by means of a control volume method and a SIMPLE algorithm. It is shown that vortex structures at the layered mode of convection have quasi-two-dimensional character.

Induction Heating of an Aluminum Billet: A Numerical Study of the Thermal Behavior

2011 ◽  
Vol 110-116 ◽  
pp. 4697-4704
Author(s):  
U. Ray ◽  
A. Sarkar ◽  
S. Sen ◽  
B. Roychowdhury ◽  
N. Barman
Keyword(s):  
Induction Heating ◽  
Source Term ◽  
Numerical Study ◽  
Control Volume ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Heating Process ◽  
Energy Conservation Equation ◽  
Transfer Behavior ◽  
Volume Method

In the present work, the heat transfer behavior during induction heating of a cylindrical aluminum billet is performed numerically. The heating process is represented by the energy conservation equation where the heat generation during heating is added as a volumetric source term. The evolution of latent heat during melting is also added as a volumetric source term. The continuity and the momentum conservation equations are considered to represent the flow field after melting starts. These governing equations are solved based on the control volume method. The enthalpy update scheme is used for evolution of melt-fraction during heating. The work predicts the evolution of temperature during heating, the distributions of temperature and melt-fraction in the domain. Subsequently, a parametric study is also performed.

Turbulent Free Convection in a Composite Enclosure

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Viviani T. Magro
Keyword(s):  
Thermal Field ◽  
Control Volume ◽  
Simple Algorithm ◽  
Flow Region ◽  
Porous Matrix ◽  
Porous Substrate ◽  
Local Flow ◽  
Vertical Walls ◽  
Energy Equations ◽  
Volume Method

This paper deals with the problem of heat transfer in square cavities partially filled with porous material. Local flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with the SIMPLE algorithm. Enhancement of convective currents within the porous substrate is detected as the Rayleigh number increases. Thin boundary layers along the cavity vertical walls and stratification of the thermal field are observed for Ra > 109.

scholarly journals Stirred tank simulation using Partially-Averaged Navier-Stokes $$k_u-\epsilon _u$$ turbulence model

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Srimanta Maji ◽  
Akshaya K. Sahu
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Power Law ◽  
Control Volume ◽  
Axial Flow ◽  
Simple Algorithm ◽  
Stirred Tank ◽  
Navier Stokes ◽  
Flow Variables ◽  
Volume Method

AbstractIn the present study, simulation of a stirred tank using axial flow impeller has been studied numerically to see the behaviour of flow variables in the entire vessel. It is assumed that the flow is steady state, two dimensional, incompressible and axisymmetric. For simulation, Partially-Averaged Navier-Stokes (PANS) $$k_u-\epsilon _u$$ k u - ϵ u turbulence model has been taken into account. For discretization, control volume method along with upwind and power-law schemes have been taken. The solutions are obtained by using the SIMPLE algorithm. The boundary conditions for impeller are given by using the experimental data. The main objective is to investigate the influence of different filters width $$f_k$$ f k of the PANS $$k_u-\epsilon _u$$ k u - ϵ u model parameter on the characteristic flow variables. The predicted results of the PANS $$k_u-\epsilon _u$$ k u - ϵ u model for different $$f_k$$ f k have been compared with the experimental data at different axial levels of the stirred tank. It has been observed that the power-law scheme gives better agreement with the experimental data. Further, near the impeller region, PANS predicted results are better for smaller $$f_k$$ f k . Also, Reynolds-Averaged Navier-Stokes Shear Stress Transport (SST) $$k-\omega $$ k - ω turbulence model has been tested for comparative study.

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