(312a) Optimization Studies Based On CFD Modeling of a Multiple Tube Reactor for Solar-Thermal Processes

A numerical model of an indirectly-irradiated solar receiver with five tubes enclosed within a reflective cavity has been developed and experimentally validated for the gasification of carbon black.  The radiation model consists of a combination of Monte Carlo and finite volume methods and is coupled with a three-dimensional CFD model treating heat, mass, momentum and species transport for the two-phase fluid/particle mixture.  This model is used to investigate the impact of factors describing receiver configuration and operating conditions on overall receiver performance. Thirteen individual factors are considered with four factors describing operating conditions (gas flow rate, carbon feed rate, solar power input, and steam to carbon ratio) and nine two-level factors describing receiver geometry.  The geometric factors are defined relative to a base design in which all tubes are arranged in a semicircle around the back cavity wall and allow for variations in cavity size, and number, radius, and arrangement of tubes with both staggered and non-staggered arrangements considered along with factors allowing for offset of all or part of the tube semicircle toward the window.  Designs are evaluated in the framework of a 2^13-8 fractional factorial design on the basis of receiver solar to chemical efficiency and reaction conversion for both absorbing and reflective cavity walls.