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Research Papers: Natural and Mixed Convection

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

[+] Author and Article Information
Watit Pakdee1

Department of Mechanical Engineering, Research Center of Microwave Utilization in Engineering (RCME), Thammasat University, Klong Luang, Pathumthani, Thailandpwatit@engr.tu.ac.th

Department of Mechanical Engineering, Research Center of Microwave Utilization in Engineering (RCME), Thammasat University, Klong Luang, Pathumthani, Thailand

1

Corresponding author.

J. Heat Transfer 133(6), 062502 (Mar 08, 2011) (8 pages) doi:10.1115/1.4003535 History: Received May 11, 2010; Revised January 14, 2011; Published March 08, 2011; Online March 08, 2011

## Abstract

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.

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## Figures

Figure 5

The temperature distributions taken at 30 s are shown to compare the numerical solutions with the experimental result

Figure 6

The temperature distributions taken at 50 s are shown to compare the numerical solutions with the experimental result

Figure 8

Centerline temperature along the z axis for uniform (dashed line) and nonuniform (solid line) porous packed beds

Figure 9

Velocity vectors from the two cases of porous medium: (a) nonuniform and (b) uniform

Figure 10

Variations of velocity magnitudes along the x axis for uniform (dashed line) and nonuniform (solid line) porous packed beds

Figure 11

Variations of u-component velocity along the x axis for uniform (dashed line) and nonuniform (solid line) porous packed beds

Figure 1

The microwave heating system with a rectangular waveguide

Figure 2

Locations of temperature measurement in the symmetrical xz plane

Figure 3

Schematic of the physical problem

Figure 4

Porosity distributions with the bead diameters: (a) 1 mm and (b) 3 mm

Figure 7

Time evolutions of temperature contour (°C) within the porous bed at 20 s, 40 s, and 60 s for uniform case ((a)–(c)) and nonuniform case ((d)–(f))

## Errata

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