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Thermal Simulations (thermal + simulation)
Selected AbstractsA fast power loss calculation method for long real time thermal simulation of IGBT modules for a three-phase inverter systemINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2006Z. Zhou Abstract A fast power losses calculation method for long real time thermal simulation of IGBT module for a three-phase inverter system is presented in this paper. The speed-up is obtained by simplifying the representation of the three-phase inverter at the system modelling stage. This allows the inverter system to be simulated predicting the effective voltages and currents whilst using large time-step. An average power losses is calculated during each clock period, using a pre-defined look-up table, which stores the switching and on-state losses generated by either direct measurement or automatically based upon compact models for the semiconductor devices. This simulation methodology brings together accurate models of the electrical systems performance, state of the art-device compact models and a realistic simulation of the thermal performance in a usable period of CPU time and is suitable for a long real time thermal simulation of inverter power devices with arbitrary load. Thermal simulation results show that with the same IGBT characteristics applied, the proposed model can give the almost same thermal performance compared to the full physically based device modelling approach. Copyright © 2006 John Wiley & Sons, Ltd. [source] Preliminary evaluation of the performance of an adsorption-based hydrogen storage systemAICHE JOURNAL, Issue 11 2009Marc-André Richard Abstract Using modeling and thermal simulations, the feasibility of an adsorption-based hydrogen storage system for vehicles is evaluated. The storage capacity of a 150 L tank filled with a high surface-area activated carbon is mapped for temperatures from 60 to 298 K and pressures up to 35 MPa. The thermal simulations are verified using experiments. For a storage capacity target of 5 kg, the adsorption-based storage system will offer a storage advantage over the cryogenic gas storage if the residual mass of hydrogen in the tank is retrieved by heating. For a discharge rate of 1.8 g/s, the required heat is of the order of 500 W. The net energy requirements for the refueling has contributions from compression, precooling and tank cooling and can approach that for liquid hydrogen storage. With a good insulation and a maximum tank pressure of 35 MPa, the dormancy period can be extended to several weeks. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Die Ermittlung des Jahresnutzkühlenergiebedarfs in Bürogebäuden mit dem Berechnungsverfahren nach Energieeinsparverordnung 2007 bzw.BAUPHYSIK, Issue 2 2009DIN V 1859 Energieinsparung; Technische Regelwerke Abstract Die seit 2007 gültige Energieeinsparverordnung (EnEV) schreibt für Bürogebäude eine gesamtheitliche Bilanzierung des Energiebedarfs vor, so dass neben dem Heizwärmeverbrauch und dem Energieverbrauch für Lüftungsanlagen erstmals auch der Kühlenergieverbrauch und der Stromverbrauch für Beleuchtung zu berücksichtigen ist. Die vorliegende Studie fokussiert auf den Jahreskühlenergieverbrauch von Büroräumen, welcher neben den Rechenregeln nach EnEV 2007 bzw. DIN V 18599 auch mit Hilfe der Algorithmen in der VDI 2067 oder mittels dynamischer, thermischer Simulationen ermittelt werden kann. Hierzu wird der Jahreskühlenergiebedarf für einen typischen Büroraum mit unterschiedlichen Fassadentypen nach den verschiedenen Verfahren berechnet, um Unterschiede aufzuzeigen. Abschließend wird exemplarisch der Einfluss des dem jeweiligen Verfahren zugrundeliegenden Außenklimas aufgezeigt. Determining the annual cooling energy demand for office buildings using the calculation procedure according to the 2007 Building Energy Conservation Ordinance or the DIN V 18599 standard. The German Building Energy Conservation Ordinance (EnEV), which has been in force since 2007, requires a holistic balance of the energy demand for office buildings, so that for the first time energy used for cooling and electricity used for lighting must be taken into account besides energy used for thermal heat and ventilation systems. This study focuses on the annual energy consumption for cooling offices which can be determined not only according to the calculation rules laid down in the EnEV 2007 or DIN V 18599 standards but also with the aid of algorithms specified in VDI 2067 or by means of dynamic thermal simulations. Here the annual energy demand for cooling a typical office with different types of facade is calculated by means of various calculation procedures in order to highlight the differences and deduce which types of facade react particularly sensitively. An example is used to illustrate the influence of the prevailing outdoor weather conditions for each procedure. [source] Dynamisch-thermisches CFD-Verfahren mit angepaßter RegelungsmethodeBAUPHYSIK, Issue 1 2007Tobias Zitzmann Dipl.-Ing. (FH) Zur Reduktion des Zeitaufwands von dynamisch-thermischen Langzeitsimulationen mit CFD-Programmen wurde in kürzlich veröffentlichten Studien eine neuartige Freeze-Flow Methode vorgestellt. Diese basiert auf der periodischen Umschaltung zwischen der volldynamischen Lösung aller Gleichungen und der ausschließlichen Lösung der Enthalpie-Gleichungen (eingefrorene Luftströmung). Dieser Artikel beschreibt eine neue, angepaßte Regelung für diese Umschaltung, wodurch eine zusätzliche Reduzierung der Simulationszeit erzielt wird. In Tests an Modellen für die mechanische und freie Lüftung sowie der freien Konvektion im geschlossenen Raum für feste und zeitveränderliche thermische Randbedingungen wurde im Vergleich zur ununterbrochenen volldynamischen Simulation eine Simulationszeiteinsparung von bis zu 93% erreicht. Dynamic thermal CFD approach using an adaptive control method. Previously published studies have presented a novel freeze-flow method for reducing CPU requirements of long-term dynamic thermal simulations using CFD programs. This works by intermittently switching between solution of the full dynamic equations and solution of the enthalpy equation only (frozen flow). This paper describes a new automated control method for this switching strategy and shows an additional decrease in simulation time. In tests with models for mechanical and natural ventilation and for free convection in a sealed room with constant and time varying thermal boundary conditions, a simulation time reduction of up to 93% was achieved when compared to a continuous fully dynamic simulation. [source] | ||||||||||