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Research Papers: Thermal Systems

CFD-Based Design of Microtubular Solid Oxide Fuel Cells

[+] Author and Article Information
Stefano Cordiner, Alessandro Mariani

Dipartimento di Ingegneria Meccanica, Università di Roma “Tor Vergata”, via del Politecnico 1, 00133 Roma, Italy

Vincenzo Mulone1

Dipartimento di Ingegneria Meccanica, Università di Roma “Tor Vergata”, via del Politecnico 1, 00133 Roma, Italymulone@ing.uniroma2.it

1

Corresponding author.

J. Heat Transfer 132(6), 062801 (Mar 19, 2010) (15 pages) doi:10.1115/1.4000709 History: Received February 13, 2009; Revised November 12, 2009; Published March 19, 2010; Online March 19, 2010

Microtubular solid oxide fuel cells (MT-SOFCs) are interesting for portable and auxiliary power units energy production systems, due to their extremely fast startup time. However, a single cell provides power in the range of 1 W, thus the number of microtubes to reach a kW scale is relevant and packaging design issues arise also. In this paper a specifically developed design procedure is presented to face with system issues and bringing into account fluid-dynamic and thermal influence on system performance. The procedure also simplifies the stack manifold design by means of a modular scale-up procedure starting from a basic optimized configuration. To this aim, a computational fluid dynamics (CFD) model has been integrated with specific models for fuel cell simulation and then validated with tailored experimental data by varying operating conditions in terms of fuel utilization and electric load. A comprehensive three–dimensional (3D) thermal-fluid-dynamic model has then been applied to the analysis of both micro-assembly (i.e., 15 tube assembly) and midi-assembly (up to 45 tubes), showing an important role of local phenomena as current homogeneity and reactant local concentration that have a strong influence on power density and temperature distribution. Microreactor power density in the range of 0.3 kW/l have been demonstrated and a specific manifold design has been realized paving the way toward a modular realization of a 1 kW MT-SOFC.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 8

Microreactor layouts (a, b, and c)

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Figure 1

Basic layout of a single-channel (3D) microtubular SOFC with a schematic description of the modeling approach on the reactive surface (1D)

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Figure 2

Basic layout (a and b) of a microreactor including the definition of the main components and geometrical parameters

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Figure 3

Basic layout of a midireactor

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Figure 4

MT-SOFC design concept

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Figure 5

Algorithm of the integrated CFD model

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Figure 6

Polarization curve comparison between experimental (▲) and numerical (◼) data

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Figure 7

H2 (a1 and b1), H2O (c1 and d1), and O2 (a2 and b2) molar fractions (%), current density (c2 and b2, A/cm2), temperature (a3 and b3 in K), and temperature gradient magnitude (c3 and d3 in K/mm) fields on the cell active surface for 100 (a and c) and 20 (b and d) N ml/minH2 flow inlet

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Figure 9

Temperature fields (K) on the active surface (row 1), O2 mole fraction (%) on a transversal section (row 2), current density fields (A/cm2) on the active surface (row 3), and temperature gradient magnitude (K/mm) fields on the active surface (row 4) for the different microreactor geometries at a constant air flow rate (10−3 kg/s). (a) Geometry A, (b) geometry B, and (c) geometry C.

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Figure 10

Temperature fields (K) on the active surface (row 1), O2 mole fraction (%) on a transversal section (row 2), current density fields (A/cm2) on the active surface (row 3) and temperature gradient magnitude (K/mm) fields on the active surface (row 4) for the different microreactor geometries at a constant maximum temperature (1260 K). (a) Geometry A, (b) geometry B, and (c) geometry C.

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Figure 11

(a) Cell position in the stack layer, related to air inlet/outlet direction. Evaluation of the relative current density (%) and relative Nusselt number (%) for each channel of (b) model A, (c) model B, and (d) model C at constant maximum temperature (1260 K) operating conditions.

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Figure 12

H2 mole fraction (%, row 1), temperature fields (K, row 2), and current distribution (A/cm2, row 3) on the active surface for geometries C (a and b) and A (c and d) at low (a and c) and high (b and d) fuel utilizations

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Figure 13

Temperature gradient magnitude on the active surface for high fuel utilization, geometries C (a) and A (b)

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Figure 14

(a) O2 molar fraction (%) field on a transversal section, (b) current density (A/cm2) on the active surface, (c) temperature (K) fields and pathlines colored by temperature on active surface and on a transversal section, and (d) temperature gradient magnitude (K/mm) field (d) on the active surface for the midireactor

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