A.R. Uribe-Ramírez

Entropy generation analysis of a SOFC by CFD: Influence of electrochemical model and its parameters

The aim of this paper is to evaluate numerically the effect of varying the electrochemical model and its parameters on the performance and entropy generation of a mono-block-layer build (MOLB) type geometry of a solid oxide fuel cell. Particularly, the influence of the exchange of current density, the electrical conductivity of the electrodes and the electrolyte has been studied and the prediction of the thermodynamic irreversibility by means of an entropy generation analysis is considered. The numerical analysis consider a 3-D CFD model that takes into account the mass transfer, heat transfer, species transport, and electrochemical reactions. Several numerical simulations were performed and each contribution to the local entropy generation rate was computed. The results show different trends of the current density, temperature, species, activation loss, ohmic loss, and concentration loss along the fuel cell. Also, the results show strong variations of the local and global entropy generation rates between the cases analyzed. It is possible to conclude that the fuel cell performance and the prediction of thermodynamic irreversibility can be significantly affected by the choice of the electrochemical models and its parameters, which must be carefully selected.

Optimal synthesis of mass exchange networks through a state-task representation superstructure

Abstract The use of mass exchange networks is a strategy that allows the recovery and reuse of dangerous components from effluents of industry, reducing, or even avoiding, the pollution derived from the release of such components to the environment. The most common strategy for the synthesis of mass exchange networks involves the use of analogies to the pinch point method for heat exchange networks, and some approaches have been reported on the use of mathematical methods to solve the synthesis problem following a super-structure based on stages. Nevertheless, such super-structure requires deciding the proper number of stages. In this work, a superstructure is proposed to represent the synthesis of a mass exchange network for the recovery of copper in an etching process. The superstructure is developed following a state-task representation, using the concepts of transfer units for the design of the mass exchangers. This representation allows obtaining a wide search space, with no need of assuming additional parameters related to the formulation. The disjunctive mathematical model is developed and its MINLP equivalent is obtained through the convex hull strategy. The MINLP is then solved using the DICOPT solver of GAMS.

Synthesis of Mass Exchange Networks: A Novel Mathematical Programming Approach

Abstract Mass integration is an efficient tool to prevent pollution derived from chemical processes. In recent years, several advances have been reported in methodologies for the design of mass exchange networks (MENs), using approaches as the pinch point and mathematical programming. Recently, simultaneous design and optimization methodologies have been proposed. The design methods based on simultaneous optimization offer the possibility of synthetizing MENs in a single step, formulating the synthesis problem as a mixed-integer nonlinear programming problem (MINLP). In this work, a MINLP model for the synthesis of mass exchange networks is presented. The model is based on a superstructure represented with disjunctions. The proposed superstructure is obtained from a state-task-network representation and is applied to a process for copper removal from an etching process. The obtained mass exchange network showed a lower total annual cost than the networks previously reported for the same process.