Eichler M.,University of Basel |
Arcones A.,TU Darmstadt |
Arcones A.,Helmholtz Center for Heavy Ion Research |
Kelic A.,Helmholtz Center for Heavy Ion Research |
And 14 more authors.
Astrophysical Journal | Year: 2015
Comparing observational abundance features with nucleosynthesis predictions of stellar evolution or explosion simulations, we can scrutinize two aspects: (a) the conditions in the astrophysical production site and (b) the quality of the nuclear physics input utilized. We test the abundance features of r-process nucleosynthesis calculations for the dynamical ejecta of neutron star merger simulations based on three different nuclear mass models: The Finite Range Droplet Model, the (quenched version of the) Extended Thomas Fermi Model with Strutinsky Integral, and the Hartree-Fock-Bogoliubov mass model. We make use of corresponding fission barrier heights and compare the impact of four different fission fragment distribution models on the final r-process abundance distribution. In particular, we explore the abundance distribution in the second r-process peak and the rare-earth sub-peak as a function of mass models and fission fragment distributions, as well as the origin of a shift in the third r-process peak position. The latter has been noticed in a number of merger nucleosynthesis predictions. We show that the shift occurs during the r-process freeze-out when neutron captures and β-decays compete and an (n,γ)-(γ,n) equilibrium is no longer maintained. During this phase neutrons originate mainly from fission of material above A = 240. We also investigate the role of β-decay half-lives from recent theoretical advances, which lead either to a smaller amount of fissioning nuclei during freeze-out or a faster (and thus earlier) release of fission neutrons, which can (partially) prevent this shift and has an impact on the second and rare-earth peak as well. © 2015. The American Astronomical Society. All rights reserved..
Hall M.,Institute Energie am Bau |
Geissler A.,Institute Energie am Bau
Bauphysik | Year: 2016
The feasibility of large net zero energy buildings. A typical net zero energy buildings has two up to four stories. The question appears if large buildings of up to 40 levels could achieve a net zero balance for HVAC only and/or achieving net zero energy building status. The analysis is based on the simulation of two multifamily dwellings and two office buildings, one each with a square and a stretched footprint. The four basic models are well insulated, equipped with a mechanical ventilation system including heat recovery and allocated with the climate of Bern-Liebefeld (average climate). A wide range of parameters is investigated in regard to their impact on the zero energy balance. The main results can be summarized as follows: - The net zero balance for HVAC only can be achieved for up to 40 levels for all variants studied but one - The four main parameters in regard to achieving a net zero energy balance are - efficient electric devices and lighting, - the type of heating system, - the actually available area for PV and - the overall efficiency of the PV-system. The results show that a net zero balance can be achieved for large multifamily dwellings and office build-ings of up to 40 levels. To this end, however, electronic devices, lighting and PV systems with a very high efficiency are necessary. This is true particularly for office buildings. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
Eichler M.,University of Basel |
Arcones A.,TU Darmstadt |
Kappeli R.,ETH Zurich |
Korobkin O.,The Oskar Klein Center |
And 8 more authors.
Journal of Physics: Conference Series | Year: 2016
We have performed r-process calculations in neutron star mergers (NSM) and jets of magnetohydrodynamically driven (MHD) supernovae. In these very neutron-rich environments the fission model of heavy nuclei has an impact on the shape of the final abundance distribution and the second r-process peak in particular. We have studied the effect of different fission fragment mass distribution models in calculations of low-Ye ejecta, ranging from a simple parametrization to extensive statistical treatments (ABLA07). The r-process path ends when it reaches an area in the nuclear chart where fission dominates over further neutron captures. The position of this point is determined by the fission barriers and the neutron separation energies of the nuclei involved. As these values both depend on the choice of the nuclear mass model, so does the r-process path. Here we present calculations using the FRDM (Finite Range Droplet Model) and the ETFSI (Extended Thomas Fermi with Strutinsky Integral) mass model with the related TF and ETFSI fission barrier predictions. Utilizing sophisticated fission fragment distribution leads to a highly improved abundance distribution. © Published under licence by IOP Publishing Ltd.
Hall M.,Institute Energie am Bau
Bauphysik | Year: 2011
More then one year the energy performance certificate of Switzerland GEAK® is well-established. In the beginning of August 2009 the GEAK® started as a public online tool. The certificate is a combination of energy performance based on calculated values and consumption data. The calculated energy demand could be validated with consumption data. The core of the certificate is an energy rating with two classifications. The classification of the efficiency building envelope describes the thermal quality of the envelope and the classification of the overall energy performance of the building describes the energy efficiency of the whole building incl. building services, lighting and appliances. The certificate contains the energy rating, the description of the building in the current state and advices for efficient improvements. In the future, proposals of cost optimized reconstructions possibilities could be done with an additionally GEAK® Plus tool. Copyright © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
Hoffmann C.,Institute Energie am Bau |
Geissler A.,Institute Energie am Bau |
Huber H.,Institute Energie am Bau
Bauphysik | Year: 2015
Bei der energetischen Gebäudeerneuerung werden oftmals nur die Fenster ausgetauscht. Wird keine mechanische Lüftungsanlage eingebaut, die einen kontinuierlichen Luftaustausch gewährleistet, können mit dichteren Fenstern Feuchtigkeitsprobleme entstehen. Abhilfe wäre mit dem Einbau von Fensterlüftern möglich. Dabei entsteht einerseits die Frage, ob diese allein in der Lage sind, den Feuchteschutzluftwechsel zu gewährleisten. Andererseits ist ungeklärt, wie hoch die möglichen Einsparungen sind, wenn man die Fensterlüfter mit einer Zu- und Abluftanlage mit Wärmerückgewinnung (WRG) vergleicht. Der Aufsatz behandelt Fensterlüfter ohne WRG in querbelüfteten Wohnungen. Thermische Simulationen einer typischen Wohnung im Mehrfamilienhaus zeigen, dass der Feuchteschutzluftwechsel allein mit Fensterlüftern nur schwer zu gewährleisten ist. In Kombination mit einer zeitgesteuerten Bedarfslüftung in Küche und Bad ist eine Deckung möglich. Allerdings müssen Fensterlüfter mit einem genügend großen Luftdurchlass eingesetzt werden (ca. 15 m3/h bei 2 Pa). Wird statt der Fensterlüfter eine Zu- und Abluftanlage mit WRG eingesetzt, so lassen sich beim ungedämmten Gebäude rund 20 % Heizenergie einsparen, beim gedämmten Gebäude sogar knapp 60 %. Passive window ventilation openings for building refurbishment. A thorough building refurbishment generally includes window replacement and thermal insulation of the opaque building envelope. However, quite often only a window replacement is done and the building envelope is left uninsulated. If there is no mechanical ventilation system installed which ensures continuous air exchange, new airtight windows usually lead to a reduced infiltration air exchanged and subsequently there may be moisture damage. A possible solution could be the integration of passive window ventilation openings (PWVO). This raises two questions: Firstly, can PWVOs guarantee the necessary ventilation rate to avoid moisture damage? Secondly, how do PWVOs compare to a ventilation system with heat recovery in terms of heating demand? This Article deals with passive window ventilation openings without heat recovery in flats with cross ventilation. Based on transient building simulation of a typical dwelling unit it is shown that the PWVOs by themselves cannot guarantee a sufficient ventilation rate for moisture control. With additional exhaust fans in the kitchen and bathroom(s) the required ventilation rate can be achieved. However, PWVOs with high air flow rates (approx. 15 m3/h at 2 Pa) must be used. Compared to PWVOs the installation of a ventilation system with heat recovery leads to energy savings of approx. 20 % in an uninsulated building. In a building where the building envelope has also been insulated, the savings would be approx. 60 %. © 2015 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.