Validation of a mathematical model for the simulation of a multitubular and multitask solar reactor

Abstract

Solar reactors represent an opportunity to obtain chemical reactions at high temperatures, saving costs in energy supply through the concentration of solar energy. Multitubular and Multitask (M&M) solar reactors are one of the options that allow the production of hydrogen and the production of synthesis gas through the gasification of hydrocarbon materials. The complexity of the phenomena involved in this type of reactor requires a robust mathematical model capable of integrating all heat transfer mechanisms. Some previous efforts made for the simulation of reactors use overly complex models that neglect some heat transfer mechanisms such as convection, and despite this have high computational cost, thus reducing the possibility of intensive debugging and the capacity of a sensitivity and uncertainty analysis. In this work, a mathematical model of distributed and transient parameters is presented that considers all the mechanisms of heat transfer by convection, radiation, and conduction in the components of a solar reactor of Multitubular and Multitask type, under a finite difference solution scheme and using the matrix method to calculate the radiation emitted from the components in 2D, offering a code with fast simulation and low computational cost. The model is validated with experimental data from the Multitubular and Multitask solar reactor, satisfactorily reproducing the prediction of the tube and wall temperatures under the conditions to which the reactor was subjected, reaching temperatures close to 1430 K in the tubes. The maximum relative error was equal to −7.4 % in the tube temperatures during a part of the experiment, acceptable given the complexity of the phenomena. The experiment lasted 180 min, and the simulation time spent around 38 s using a commercial computing processor. The model has the ability to quickly and satisfactorily reproduce the behavior of a Multitubular and Multitask type solar reactor, taking into account all the heat transfer mechanisms that had been omitted in previous works.