Transient behavior of a multi-tubular cavity solar thermochemical reactor

• Published in: Applied thermal engineering 2017-08, Vol.123, p.1255-1262
• Main Authors: Valadés-Pelayo, Patricio J., Arancibia-Bulnes, Camilo A.
• Format: Article
• Language: English
• Subjects: Computer simulation; Convection heating; Heat transfer; Iterative methods; Monte Carlo; Monte Carlo simulation; Radiative transfer; Ramps; Random walk; Reactors; Solar energy; Solar furnace; Solar reactor; Three dimensional models; Transient heat transfer; Tubes
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2017.05.192

•Three-dimensional heat transfer in a multi-tubular cavity solar reactor is modeled.•A suspension of CeO2 particles in Argon flows through the reactor tubes.•Time dependent temperature gradients in the tubes and gas-particle media are studied.•Gradients are mainly angular during heating, but they become axial in steady-state.•Progressive heating ramps reduce transient thermal gradients and thermal stress. A three-dimensional transient heat transfer model is presented to predict the start-up operation of a multi-tubular cavity reactor under concentrated irradiation in a solar furnace. The reactor consists of a cavity containing nine absorber tubes, through which a suspension of CeO2 in Argon flows. An iterative splitting scheme coupling a Continuous Random Walk, a Finite Volume, and a Ray-Tracing Monte Carlo methods, is implemented to estimate the temperature gradients in the tubes and gas-particle media. The radiation heat transfer among the tubes and cavity walls is considered, as well as conduction and convection in the tubes and the particle suspension. During the initial heating stage, gradients are mainly angular, while in steady-state they are primarily axial. The former may cause tube bending or cracking, and strategies to reduce them are examined. In particular, different heating ramps were simulated, which was found to reduce these initial thermal gradients.