Modeling Fixed Bed Membrane Reactors for Hydrogen Production through Steam Reforming Reactions: A Critical Analysis

Membrane reactors for hydrogen production have been extensively studied in the past years due to the interest in developing systems that are adequate for the decentralized production of high-purity hydrogen. Research in this field has been both experimental and theoretical. The aim of this work is two-fold. On the one hand, modeling work on membrane reactors that has been carried out in the past is presented and discussed, along with the constitutive equations used to describe the different phenomena characterizing the behavior of the system. On the other hand, an attempt is made to shed some light on the meaning and usefulness of models developed with different degrees of complexity. The motivation has been that, given the different ways and degrees in which transport models can be simplified, the process is not always straightforward and, in some cases, leads to conceptual inconsistencies that are not easily identifiable or identified

Arc tracking control in insulation systems for aeronautic applications: challenges, opportunities, and research needs

Next generation aircrafts will use more electrical power to reduce weight, fuel consumption, system complexity and greenhouse gas emissions. However, new failure modes and challenges arise related to the required voltage increase and consequent rise of electrical stress on wiring insulation materials, thus increasing the risk of electrical arc appearance. This work performs a critical and comprehensive review concerning arc tracking effects in wiring insulation systems, underlying mechanisms, role of materials and possible mitigation strategies, with a special focus on aircraft applications. To this end an evaluation of the scientific and technological state of the art is carried out from the analysis of theses, research articles, technical reports, international standards and white papers. This review paper also reports the limitations of existing insulation materials, standard test methods and mitigation approaches, while identifying the research needs to comply with the future demands of the aircraft industryPeer ReviewedPostprint (published version

Biomimetic flow fields for proton exchange membrane fuel cells: A review of design trends

Bipolar Plate design is one of the most active research fields in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) development. Bipolar Plates are key components for ensuring an appropriate water management within the cell, preventing flooding and enhancing the cell operation at high current densities. This work presents a literature review covering bipolar plate designs based on nature or biological structures such as fractals, leaves or lungs. Biological inspiration comes from the fact that fluid distribution systems found in plants and animals such as leaves, blood vessels, or lungs perform their functions (mostly the same functions that are required for bipolar plates) with a remarkable efficiency, after millions of years of natural evolution. Such biomimetic designs have been explored to date with success, but it is generally acknowledged that biomimetic designs have not yet achieved their full potential. Many biomimetic designs have been derived using computer simulation tools, in particular Computational Fluid Dynamics (CFD) so that the use of CFD is included in the review. A detailed review including performance benchmarking, time line evolution, challenges and proposals, as well as manufacturing issues is discussed.Ministerio de Ciencia, Innovación y Universidades ENE2017-91159-EXPMinisterio de Economía y Competitividad UNSE15-CE296

How does the franchisor’s choice of different control mechanisms affect franchisees’ and employee-managers’ satisfaction?

Satisfaction of franchisees and employee-managers affects the overall performance of a franchise system. We argue that different actors in the same franchise system need to be treated in different ways. The franchisor’s choice of control mechanisms affects the satisfaction of franchisees and employee-managers differently. Drawing on data from the largest German franchise system, we show that the effectiveness of different control mechanisms depends on actor type and experience. Outcome control leads to higher satisfaction among franchisees and employee-managers, while behavior control enhances employee-managers’ satisfaction. Thereby, outcome control leads to higher satisfaction among more experienced franchisees, while behavior control enhances both highly and lowly experienced employee-managers’ satisfaction. Our results suggest that franchisors face a dilemma: On the one hand, behavior control is associated with high costs and has no impact on franchisees’ satisfaction at all. On the other hand, it might still be necessary to prevent franchisees from behaving opportunistically

Approximation of System Components for Pump Scheduling Optimisation

© 2015 The Authors. Published by Elsevier Ltd.The operation of pump systems in water distribution systems (WDS) is commonly the most expensive task for utilities with up to 70% of the operating cost of a pump system attributed to electricity consumption. Optimisation of pump scheduling could save 10-20% by improving efficiency or shifting consumption to periods with low tariffs. Due to the complexity of the optimal control problem, heuristic methods which cannot guarantee optimality are often applied. To facilitate the use of mathematical optimisation this paper investigates formulations of WDS components. We show that linear approximations outperform non-linear approximations, while maintaining comparable levels of accuracy

How does the franchisor’s choice of different control mechanisms affect franchisees’ and employee-managers’ satisfaction?

Satisfaction of franchisees and employee-managers affects the overall performance of a franchise system. We argue that different actors in the same franchise system need to be treated in different ways. The franchisor’s choice of control mechanisms affects the satisfaction of franchisees and employee-managers differently. Drawing on data from the largest German franchise system, we show that the effectiveness of different control mechanisms depends on actor type and experience. Outcome control leads to higher satisfaction among franchisees and employee-managers, while behavior control enhances employee-managers’ satisfaction. Thereby, outcome control leads to higher satisfaction among more experienced franchisees, while behavior control enhances both highly and lowly experienced employee-managers’ satisfaction. Our results suggest that franchisors face a dilemma: On the one hand, behavior control is associated with high costs and has no impact on franchisees’ satisfaction at all. On the other hand, it might still be necessary to prevent franchisees from behaving opportunistically

Hygrothermal Performance of Worship Spaces: Preservation, Comfort and Energy Consumption

The energy problem, one the most important on a global scale, greatly affects the environment. Much of the current energy consumption occurs in existing buildings, including heritage buildings with varying protected status. Energy intervention and heritage conservation conflict to some extent, as research focuses more on the search for improved energy efficiency solutions for materials and systems than on their application to heritage buildings. This study describes experimental research on environmental conditioning techniques in spaces of worship in a temperate climate in southern Spain. Buildings were monitored and assessed in the implementation of different environmental techniques—active and combined (passive and active)—with the aim of improving the thermal comfort conditions of the faithful while preserving the cultural heritage of these buildings. The need for a control system of RH and the air system was concluded, as well as radiant floors and radiators, which, in the considered case studies, would barely affect the artworks. 24- and 12-h operation are better suited to heritage preservation than occasional use. All operation schedules are valid for thermal comfort.Universidad de Malaga Universidad de Sevill

Dynamic simulation model of trans-critical carbon dioxide heat pump application for boosting low temperature distribution networks in dwellings

This research investigates the role of new hybrid energy system applications for developing a new plant refurbishment strategy to deploy small scale smart energy systems. This work deals with a dynamic simulation of trans-critical carbon dioxide heat pump application for boosting low temperature distribution networks to share heat for dwellings. Heat pumps provide high temperature heat to use the traditional emission systems. The new plant layout consists of an air source heat pump, four trans-critical carbon dioxide heat pumps (CO2-HPs), photovoltaic arrays, and a combined heat and power (CHP) for both domestic hot water production and electricity to partially drive the heat pumps. Furthermore, electric storage devices adoption has been evaluated. That layout has been compared to the traditional one based on separated generation systems using several energy performance indicators. Additionally, a sensitivity analysis on the primary energy saving, primary fossil energy consumptions, renewable energy fraction and renewable heat, with changes in building power to heat ratios, has been carried out. Obtained results highlighted that using the hybrid system with storage device it is possible to get a saving of 50% approximately. Consequently, CO2-HPs and hybrid systems adoption could be a viable option to achieve Near Zero Energy Building (NZEB) qualification