Simultaneous synthesis of heat exchanger networks with pressure recovery: optimal integration between heat and work

The optimal integration between heat and work may significantly reduce the energy demand and consequently the process cost. This paper introduces a new mathematical model for the simultaneous synthesis of heat exchanger networks (HENs) in which the pressure levels of the process streams can be adjusted to enhance the heat integration. A superstructure is proposed for the HEN design with pressure recovery, developed via generalized disjunctive programming (GDP) and mixed-integer nonlinear programming (MINLP) formulation. The process conditions (stream temperature and pressure) must be optimized. Furthermore, the approach allows for coupling of the turbines and compressors and selection of the turbines and valves to minimize the total annualized cost, which consists of the operational and capital expenses. The model is tested for its applicability in three case studies, including a cryogenic application. The results indicate that the energy integration reduces the quantity of utilities required, thus decreasing the overall cost.

MINLP Model for the Synthesis of Heat Exchanger Networks with Handling Pressure of Process Streams

This paper introduces a new mathematical model for the simultaneous synthesis of heat exchanger networks (HENs), wherein the handling pressure of process streams is used to enhance the heat integration. The proposed approach combines generalized disjunctive programming (GDP) and mixed-integer nonlinear programming (MINLP) formulation, in order to minimize the total annualized cost composed by operational and capital expenses. A multi-stage superstructure is developed for the HEN synthesis, assuming constant heat capacity flow rates and isothermal mixing, and allowing for streams splits. In this model, the pressure and temperature of streams must be treated as optimization variables, increasing further the complexity and difficulty to solve the problem. In addition, the model allows for coupling of compressors and turbines to save energy. A case study is performed to verify the accuracy of the proposed model. In this example, the optimal integration between the heat and work decreases the need for thermal utilities in the HEN design. As a result, the total annualized cost is also reduced due to the decrease in the operational expenses related to the heating and cooling of the streams.

Percepción, activos intangibles y stakeholders: modelo para el análisis de imagen corporativa

El presente artículo abordará aproximaciones para la gestión de la imagen corporativa; pensada como un activo intangible que proyecta la institución. Además, se consideran diversos modelos y conceptos de capital intelectual que identifican factores relevantes hacia la toma decisión por parte de stakeholders. La percepción de imagen es un tema que ha suscitado interés por parte de instituciones, pues ésta se encuentra estrechamente vinculada a la formación integral de una idea que influye en el desarrollo de una actitud favorable o no hacia la reputación corporativa. De esta manera, los clientes, consumidores, proveedores, colaboradores, entre otros; reciben a través de distintas formas elementos que le ayudan a conformar una idea sobre la institución mediante sus percepciones; por lo que, orientar los esfuerzos y acciones en torno a este intangible, dará como resultado una rentabilidad no sólo monetaria sino una fidelidad y confianza por parte de sus stakeholders. Es así, que se ha visto la necesidad de proponer un modelo para el análisis de la imagen corporativa de instituciones, el mismo que consta de cinco categorías las cuales poseen parámetros de puntuación, construidos a partir de los aportes de diferentes autores.

Life-cycle portfolio choice with liquid and illiquid financial assets

Traditionally, quantitative models that have studied households׳ portfolio choices have focused exclusively on the different risk properties of alternative financial assets. We introduce differences in liquidity across assets in the standard life-cycle model of portfolio choice. More precisely, in our model, stocks are subject to transaction costs, as considered in recent macroliterature. We show that when these costs are calibrated to match the observed infrequency of households׳ trading, the model is able to generate patterns of portfolio stock allocation over age and wealth that are constant or moderately increasing, thus more in line with the existing empirical evidence.