Table of Contents
Journal of Powder Technology
Volume 2015 (2015), Article ID 293165, 9 pages
http://dx.doi.org/10.1155/2015/293165
Research Article

Wall-to-Suspension Heat Transfer in a CFB Downcomer

1Department of Chemical Engineering, Bio- & Chemical Systems Technology, Reactor Engineering and Safety Section, KU Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
2Department of Chemical Engineering, Process and Environmental Technology Lab, KU Leuven, Jan De Nayerlaan 5, 2860 Sint-Katelijne-Waver, Belgium
3School of Engineering, University of Warwick, Coventry CV4 7AL, UK

Received 21 June 2015; Revised 11 August 2015; Accepted 18 August 2015

Academic Editor: Franco Berruti

Copyright © 2015 Huili Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

With the development of circulating fluidized beds (CFB) and dense upflow bubbling fluidized beds (UBFB) as chemical reactors, or in the capture and storage of solar or waste heat, the associated downcomer has been proposed as an additional heat transfer system. Whereas fundamental and applied research towards hydrodynamics has been carried out, few results have been reported on heat transfer in downcomers, even though it is an important element in their design and application. The wall-to-suspension heat transfer coefficient (HTC) was measured in the downcomer. The HTC increases linearly with the solids flux, till values of about 150 kg/m2 s. The increasing HTC with increasing solid circulation rate is reflected through a faster surface renewal by the downflow of the particle-gas suspension at the wall. The model predictions and experimental data are in very fair agreement, and the model expression can predict the influence of the dominant parameters of heat transfer geometry, solids circulation flow, and particle characteristics.