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RESEARCH PAPERS: Bubbles, Particles and Droplets

An Experimental Investigation of the Influence of Gas and Solid Particle Interaction on the Heat Transfer Effectiveness of a Falling-Bed Heat Exchanger

[+] Author and Article Information
Matthew J. Frain

Department of Mechanical and Industrial Engineering,  University of Massachusetts Amherst, Engineering Laboratory, Box 32210, Amherst, MA 01003-2210

David P. Schmidt

Department of Mechanical and Industrial Engineering,  University of Massachusetts Amherst, Engineering Laboratory, Box 32210, Amherst, MA 01003-2210schmidt@ecs.umass.edu

Woodrow A. Fiveland

 ALSTOM Power Inc., 2000 Day Hill Road, Windsor, CT 06095

J. Heat Transfer 127(10), 1077-1086 (May 13, 2005) (10 pages) doi:10.1115/1.2033904 History: Received November 03, 2004; Revised May 13, 2005

The objective of this investigation is to quantify and understand the performance of falling-bed heat exchangers. Experimental steady-state heat transfer data, whose quality is demonstrated with an accurate energy balance between the gas and particle streams, are presented. Measured temperatures, pressures, and overall heat transfer rates are compared to predicted values from a one-dimensional analytical model, and the capabilities and deficiencies of the model are discussed. In addition, the effect of a particle distributor on the performance of the falling-bed heat exchanger is measured. While the model is shown to be unable to provide a quantitatively accurate prediction of the performance of the heat exchanger, it does provide an estimate of the maximum possible effectiveness of the heat exchanger. A simple particle distributor is shown to provide relatively poor effectiveness, while the use of a more complex distributor causes the effectiveness of the heat exchanger to approach the upper bound. The combination of experimental data and model results offers useful insight for developing falling-bed heat exchangers and provides a useful test case for future modeling efforts.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 5

Comparison of measured gas and particle heat transfer rates to predictions of uniform mixing model

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Figure 6

Axial temperature profiles for tests with simple particle injection. Measured temperatures (symbols) plotted against prediction of uniform mixing model (solid line). The respective particle and gas mass flow rates are (a) 1.05 and 0.45kg∕s, (b) 0.67 and 0.46kg∕s, and (c) 0.39 and 0.44kg∕s.

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Figure 8

Radial temperature profiles for tests with simple particle injection. The solid vertical line is the location of the column wall. The respective particle and gas mass flow rates are (a) 1.05 and 0.45kg∕s, (b) 0.67 and 0.46kg∕s, and (c) 0.39 and 0.44kg∕s.

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Figure 9

Axial gas temperature profiles for tests with basket distributor. Measured temperatures (symbols) plotted against prediction of uniform mixing model (solid line). The respective particle and gas mass flow rates are (a) 0.94 and 0.47kg∕s, (b) 0.58 and 0.45kg∕s, and (c) 0.28 and 0.45kg∕s.

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Figure 10

Axial pressure profiles for tests with basket distributor. Measured pressures plotted against prediction of uniform mixing model (black line). Open symbols are the sum of the measured pressure differences up to that elevation. The gray symbol is the pressure difference over the entire column. The respective particle and gas mass flow rates are (a) 0.94 and 0.47kg∕s, (b) 0.58 and 0.45kg∕s, and (c) 0.28 and 0.45kg∕s.

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Figure 11

Comparison of apparent experimental effectiveness of falling-bed heat exchanger with and without basket distributor to uniform mixing model as a function of ratio of particle to gas stream thermal capacities. Vertical gray line indicates a capacitance ratio Cr of one. Dotted line represents the uniform mixing model assuming a constant specific heat of bauxite.

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Figure 1

ALSTOM power plant laboratory enhanced heat transfer (EHT) facility

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Figure 2

Image of particle flow from the basket distributor. Grid squares are 2.54cm(1in.) wide.

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Figure 3

Photograph of 700μm bauxite. Scale gradation is in increments of 60μm.

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Figure 4

Heat transfer rate balance between gas and particles

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Figure 7

Axial pressure profiles for tests with simple particle injection. Measured pressures plotted against prediction of uniform mixing model (black line) and hydrostatic gradient of air only (gray line). Open symbols are the sum of the measured pressure differences up to that elevation. The gray symbol is the pressure difference over the entire column. The respective particle and gas mass flow rates are (a) 1.05 and 0.45kg∕s, (b) 0.67 and 0.46kg∕s, and (c) 0.39 and 0.44kg∕s.

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