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TECHNICAL PAPERS: Heat Transfer Enhancement

Heat Transfer Enhancement of Steam Reformation by Passive Flow Disturbance Inside the Catalyst Bed

[+] Author and Article Information
Paul Anders Erickson

Mechanical and Aeronautical Engineering Department,  University of California, Davis, One Shield Avenue, Davis, CA 95616paerickson@ucdavis.edu

Chang-Hsien Liao

Mechanical and Aeronautical Engineering Department,  University of California, Davis, One Shield Avenue, Davis, CA 95616

J. Heat Transfer 129(8), 995-1003 (Oct 06, 2006) (9 pages) doi:10.1115/1.2728906 History: Received January 11, 2006; Revised October 06, 2006

Because of the potential for high efficiency and low emissions, hydrogen powered systems are considered to be the next generation power source for both stationary and transportation applications. Providing a hydrogen source is a critical challenge. Steam reforming processes are demonstrated for producing hydrogen for fuel cell and other applications. Generating hydrogen via steam reformation requires that heat energy be transferred to the reactants to support the endothermic reaction. For a cylindrical steam-reforming reactor, large thermal gradients between the heat source (reactor wall) and reactor centerline create a nonideal condition for complete conversion. This gradient is caused by insufficient heat transfer inside the catalyst bed. Passive flow disturbance inside the catalyst bed is a potential method to enhance the heat and mass transfer in the steam-reforming process. This paper presents experimental research that investigates the effect of changing the flow pathway inside the reactor to improve the heat and mass transfer and thus enhance fuel conversion. Based on the experimental results, a 14% increase of methanol fuel conversion was achieved via the passive flow disturbance enhancement. The tradeoff was an extra pressure drop of 2.5 kPa across the reactor. A 30 h experimental run does not show a significant change in degradation rate for the passive flow disturbance. The results of this study contribute to the improvement of reformer design for better fuel processing system performance.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Simplified schematic of heat conducting into a nonobstructed cylindrical catalyst bed and a typical temperature profile in the radial direction

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Figure 2

Steps required within the catalytic steam-reformation process (6)

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Figure 3

Schematic of catalyst bed obstructed with two packages of bluff bodies

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Figure 4

Scheme of minimum path length inside: (a) nonobstructed reactor; and (b) reactor with bluff bodies

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Figure 5

Regions of mass transfer-limited and reaction-limited reactions for a single particle (10)

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Figure 6

Potential channeling effect inside a catalyst bed

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Figure 7

Schematic of reaction in pipe cross section, Tw>Tc

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Figure 8

Decreasing channeling effect by introducing flow obstruction

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Figure 9

General schematic of the methanol reforming system

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Figure 10

Methanol conversion as a function of space velocity (lhsvm, h−1) with pelletized catalyst

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Figure 11

Methanol conversion as a function of space velocity (lhsvm, h−1) with crushed catalyst

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Figure 12

Temperature profile along the axial direction inside a pelletized catalyst bed

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Figure 13

Temperature profile along the axial direction inside a crushed catalyst bed

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Figure 14

Pressure drop at different upstream pressures (flow rates)

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Figure 15

Catalyst degradation rate comparison of crushed catalyst bed with eight sets of bluff body and without bluff body

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