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Engineering Tools (engineering + tool)
Selected AbstractsAlong-channel mathematical modelling for proton exchange membrane fuel cellsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2005Wenbo Huang Abstract Proper water and thermal management is essential for obtaining high performance of proton exchange membrane fuel cells (PEMFCs). A steady, two-dimensional water and thermal management model was developed, aiming at considering pressure effects (i.e. the effects of local pressure on the cell performance), pressure drop, open circuit voltage variation with stack temperature, water vapour effects on membrane conductivity, which made the model physically more reasonable and more suitable for various operating conditions. The model could predict the distributions of a series of important parameters along the flow channel, and thus the effects of various operating and design parameters on the fuel cell performance could be investigated easily by numerical trial-and-error method. The modelling results compared well with the available experimental results from the literatures. The results also showed that the humidification of both anode and cathode is crucial for the performance of PEMFCs. The model could be a very useful engineering tool for the optimization of PEMFCs. Copyright © 2005 John Wiley & Sons, Ltd. [source] From discovery to data: What must happen for molecular simulation to become a mainstream chemical engineering toolAICHE JOURNAL, Issue 6 2009Edward J. Maginn First page of article [source] New approach for the analysis and design of negative-resistance oscillators: Application to a quasi-MMIC VCOINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2006Jeffrey Chuan Abstract This article proposes a new approach for the analysis and design of negative-resistance oscillators using computer-aided engineering tools. The method presented does not require any special probe and makes the oscillator design similar to the methodology applied to amplifiers. It speeds up convergence and avoids uncertainties in the solution. The negative-resistance oscillator is split into two parts: an active-amplifying part and a resonator part. A chain is constructed by linking both parts and repeating them several times, which is known as the repeated circuit simulation procedure. This method allows the separation of the signal flowing between them. Small-signal AC-sweep and harmonic-balance techniques, both available in several commercial software packages, are applied. This method is theoretically justified and shows convergence with less iteration. Furthermore, it is more robust than standard harmonic-balance probes in the case of multiple frequencies of oscillation. It has been demonstrated in the design of a quasi-MMIC VCO. This VCO has an external resonator circuit (coaxial resonator and varactor) and a MMIC negative-resistance circuit, which was manufactured using ED02AH p-HEMT technology (OMMIC). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source] Comprehensive process design study for layered-NOX -control in a tangentially coal fired boilerAICHE JOURNAL, Issue 3 2010Wei Zhou Abstract As emissions regulations for coal-fired power plants become stricter worldwide, layering combustion modification and post-combustion NOX control technologies can be an attractive option for efficient and cost-effective NOX control in comparison to selective catalytic reduction (SCR) technology. The layered control technology approach designed in this article consists of separate overfire air (SOFA), reburn, and selective noncatalytic reduction (SNCR). The combined system can achieve up to 75% NOX reduction. The work presented in this article successfully applied this technology to NRG Somerset Unit 6, a 120-MW tangential coal-fired utility boiler, to reduce NOX emissions to 0.11 lb/MMBtu (130 mg/Nm3), well under the US EPA SIP Call target of 0.15 lb/MMBtu. The article reviews an integrated design study for the layered system at Somerset and evaluates the performance of different layered-NOX -control scenarios including standalone SNCR (baseline), separated overfire air (SOFA) with SNCR, and gas reburn with SNCR. Isothermal physical flow modeling and computational fluid dynamics simulation (CFD) were applied to understand the boiler flow patterns, the combustible distributions and the impact of combustion modifications on boiler operation and SNCR performance. The modeling results were compared with field data for model validation and verification. The study demonstrates that a comprehensive process design using advanced engineering tools is beneficial to the success of a layered low NOX system. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Zur Diskussion des Böenreaktionsfaktors G nach DIN 1055-4:2005BAUTECHNIK, Issue 10 2009BayIKBau Robert Hertle Dr.-Ing., Beratender Ingenieur VBI, Prüfingenieur für Standsicherheit vpi Allgemeines; Baumechanik; General Topics; Structural Mechanics Abstract Mit Einführung der DIN 1055-4:2005 fand ein Paradigmenwechsel bei der Beschreibung der Windlasten statt. Das bisherige, deterministische Konzept zur Definition der Windeinwirkung wurde verlassen und durch ein auf stochastischen Überlegungen fußendes ersetzt. Für Konstruktionen und Bauwerke, die nicht schwingungsanfällig unter böigen Windeinwirkungen sind, ergeben sich daraus keine nennenswerten Änderungen bei der rechnerischen Untersuchung. Für die Analyse von schwingungsanfälligen Konstruktionen hat diese Neukonzeption tiefgreifende Konsequenzen. Die bekannte und einfach zu handhabende Ermittlung des Böenreaktionsfaktors auf Grundlage der Normen der achtziger und neunziger Jahre des vergangenen Jahrhunderts wurde durch ein komplexes, unübersichtliches und mit einfachen Ingenieurmethoden nicht mehr zu überprüfendes Berechnungsschema abgelöst. In diesem Beitrag wird dieses Schema diskutiert, und es wird ein einfaches Näherungsverfahren zur Ermittlung der Böenreaktion einer Konstruktion vorgeschlagen, welches, insbesondere vor dem Hintergrund der sonstigen Unschärfen und Unsicherheiten einer Berechnung, ausreichende Genauigkeit zeigt. On the discussion of the gust reaction factor acc. DIN 1055-4:2005. With the introduction of DIN 1055-4:2005 a change of paradigm concerning the description of wind loads took place. The previous concept, based on a deterministic view, was replaced by an approach using stochastic considerations. For constructions and buildings deemed to be not susceptible to gust action, no significant changes within the structural analysis arise. Enormous consequences, on the other hand, have to be faced when analyzing structures susceptible to gust action. The well known and easy to handle method for calculating the gust reaction factor using the standards of the 80th and 90th of the last century, was redeemed by a complex, partly confused calculation scheme which is not checkable with usual engineering tools. In the following paper this calculation scheme is discussed. Following to this discussion, a simplified method for calculating the gust reaction factor is presented. The accuracy of this method lies, having the usual uncertainties and deficits of structural analyses in mind, in an acceptable range. [source] An Introduction to Simulation and Visualization of Biological Systems at Multiple Scales: A Summer Training Program for Interdisciplinary ResearchBIOTECHNOLOGY PROGRESS, Issue 1 2006Rajan Munshi Advances in biomedical research require a new generation of researchers having a strong background in both the life and physical sciences and a knowledge of computational, mathematical, and engineering tools for tackling biological problems. The NIH-NSF Bioengineering and Bioinformatics Summer Institute at the University of Pittsburgh (BBSI @ Pitt;www.ccbb.pitt.edu/bbsi) is a multi-institutional 10-week summer program hosted by the University of Pittsburgh, Duquesne University, the Pittsburgh Supercomputing Center, and Carnegie Mellon University, and is one of nine Institutes throughout the nation currently participating in the NIH-NSF program. Each BBSI focuses on a different area; the BBSI @ Pitt, entitled "Simulation and Computer Visualization of Biological Systems at Multiple Scales", focuses on computational and mathematical approaches to understanding the complex machinery of molecular-to-cellular systems at three levels, namely, molecular, subcellular (microphysiological), and cellular. We present here an overview of the BBSI@Pitt, the objectives and focus of the program, and a description of the didactic training activities that distinguish it from other traditional summer research programs. Furthermore, we also report several challenges that have been identified in implementing such an interdisciplinary program that brings together students from diverse academic programs for a limited period of time. These challenges notwithstanding, presenting an integrative view of molecular-to-system analytical models has introduced these students to the field of computational biology and has allowed them to make an informed decision regarding their future career prospects. [source] | ||||||||||