Winteler, Christian

Winteler, Christian


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  • Publikation
    The Role of Fission in Neutron Star Mergers and Its Impact on the r-Process Peaks
    (The American Astronomical Society, 15.07.2015) Eichler, Marius; Arcones, Almudena; Kelic, Alexandra; Korobkin, Oleg; Langanke, Karlheinz; Marketin, Tomislav; Martinez-Pinedo, Gabriel; Panov, Igor; Rauscher, Thomas; Rosswog, Stephan; Winteler, Christian; Zinner, Nikolaj; Thielemann, Friedrich-Karl [in: The Astrophysical Journal]
    Comparing observational abundance features with nucleosynthesis predictions of stellar evolution or explosion simulations 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 (FRDM), the (quenched version of the) Extended Thomas Fermi Model with Strutinsky Integral (ETFSI-Q), and the Hartree-Fock-Bogoliubov (HFB) 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 not maintained anymore. 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.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Publikation
    Seasonal Performance of a Combined Solar, Heat Pump and Latent Heat Storage System
    (Ecole Polytechnique Fédérale de Lausanne (EPFL), 2013) Winteler, Christian; Dott, Ralf; Afjei, Thomas; Scartezzini, Jean-Louis [in: Proceedings of CISBAT 2013]
    This paper investigates the seasonal performance of a combined solar, heat pump and latent heat storage system for dwellings. This combination could provide a viable alternative to common brine-water heat pump systems with a borehole heat exchanger (BHX). Since the latent heat storage, or ice storage, is filled with pure water, it can also be used in (but is not limited to) places where a BHX is prohibited, e.g. water protection areas. The aim of this work is to find and evaluate given system configurations for three different annual heat demands that reach seasonal performance factors (SPF) comparable to those of BHX heat pump systems, i.e. SPF ~ 4.0. A simulation study using MATLAB®/SIMULINK® and the CARNOT Blockset is conducted. Technologies considered in the simulation study are a brine-water heat pump, unglazed solar collectors as source for the heat pump and a buried ice storage that serves as alternative source for the heat pump and is regenerated by the collectors. Unglazed collectors use solar irradiation and ambient heat (via convective heat exchange) for heat generation. Additionally, thermal coupling of the ice storage to the surrounding soil which also contributes to the regeneration of the system is considered. The simulation models of this system have been validated with laboratory and field test data. The heat generated by the heat pump is used for space heating and domestic hot water preparation of single family houses with different heat loads which have been defined in the framework of IEA SHC Task 44 / HPP Annex 38 "Solar and heat pump systems". To obtain the desired SPF for each building type the power output of the heat pump with the corresponding size of the collector field is varied. For each building a configuration is found that yields a SPF ~ 4.0. A high SPF can only be reached as long as no backup heating is needed, which means, that the ice storage should never be completely discharged, i.e. completely frozen. This requires significant contributions from the solar collector, especially during the heating period.
    04B - Beitrag Konferenzschrift