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RESEARCH PAPERS: Radiative Properties

Tomography-Based Heat and Mass Transfer Characterization of Reticulate Porous Ceramics for High-Temperature Processing

[+] Author and Article Information
Sophia Haussener

Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland

Patrick Coray

Solar Technology Laboratory, Paul Scherrer Institute, 5232 Villigen, Switzerland

Wojciech Lipiński

Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455

Peter Wyss

Department of Electronics/Metrology, EMPA Material Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland

Aldo Steinfeld1

Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland; and Solar Technology Laboratory, Paul Scherrer Institute, 5232 Villigen, Switzerlandaldo.steinfeld@ethz.ch

1

Corresponding author.

J. Heat Transfer 132(2), 023305 (Dec 03, 2009) (9 pages) doi:10.1115/1.4000226 History: Received October 31, 2008; Revised April 29, 2009; Published December 03, 2009; Online December 03, 2009

Reticulate porous ceramics employed in high-temperature processes are characterized for heat and mass transfer. The exact 3D digital geometry of their complex porous structure is obtained by computer tomography and used in direct pore-level simulations to numerically calculate their effective transport properties. Two-point correlation functions and mathematical morphology operations are applied for the geometrical characterization that includes the determination of porosity, specific surface area, representative elementary volume edge size, and mean pore size. Finite volume techniques are applied for conductive/convective heat transfer and flow characterization, which includes the determination of the thermal conductivity, interfacial heat transfer coefficient, permeability, Dupuit–Forchheimer coefficient, residence time, tortuosity, and diffusion tensor. Collision-based Monte Carlo method is applied for the radiative heat transfer characterization, which includes the determination of the extinction coefficient and scattering phase function.

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Figures

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Figure 1

Sample of RPC foam: (a) top view photograph and (b) 3D surface rendering of 15 μm voxel size tomography data

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Figure 2

Normalized histograms of the absorption values for the scans with 30 μm (dotted line) and 15 μm (solid line) voxel sizes. The points indicate the corresponding threshold values of αt/αmax=0.39 and 0.23.

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Figure 3

Normalized threshold absorption values for 36 subelements of three selected tomograms for voxel sizes of 30 μm and 15 μm

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Figure 4

(a) Tomogram of a single strut obtained by HRCT; (b) magnified fragment of the strut edge marked with the white frame in Fig. 4

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Figure 5

Opening pore size distribution of the RPC foam for the 30 μm (solid curve) and 15 μm (dotted curve) voxel size tomography data

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Figure 6

(a) Variation in computed and measured incident radiative intensities as a function of normalized path length in the sample; (b) scattering phase functions of the RPC foam, IOTS, and of large diffuse opaque spheres as a function of the cosine of scattering angle

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Figure 7

Experimental spectroscopy setup: (1) dual Xe-Arc/Cesiwid-Glowbar lamp, (2) double monochromator, ((3) and (5)) collimating and focusing lens pairs, (4) sample mounted on a linear positioning stage, (6) detector, (7) optical chopper, (8) lock-in amplifier, (9) data acquisition system

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Figure 8

(a) Contour map of the normalized temperature distribution (T−T2)/(T1−T2) along the axis perpendicular to the temperature boundary condition of the RPC foam (thick solid lines depict solid-fluid phase boundary) for kf/ks=1.0×10−4; (b) the effective thermal conductivity of the RPC foam and of parallel and serial slabs at ε=0.91

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Figure 9

Computed (points) and fitted (lines) Nu number as a function of Re and Pr numbers

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Figure 10

Normalized porosity, extinction coefficient, and effective conductivity for cubic volumes with edge lengths l

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Figure 11

Dimensionless pressure gradient as a function of Re number

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Figure 12

(a) Tortuosity and (b) residence time distributions for four selected Re numbers of fluid flow through the RPC foam

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Figure 13

Mean residence time as a function of Re number

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Figure 14

Normalized dispersion tensor as a function of Re for the RPC foam

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