Eismann, Ralph

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Eismann
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Ralph
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Eismann, Ralph

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2015 - 20197
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Enddatum: 2019 × Anfangsdatum: 2015 ×

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Gerade angezeigt 1 - 7 von 7
  • Vorschaubild
    Publikation
    Cost reduction of solar thermal plants by advanced thermalhydraulic design methods
    (IOP Publishing, 04.09.2019) Eismann, Ralph; Scartezzini, Jean-Louis [in: CISBAT]
    04B - Beitrag Konferenzschrift
  • Vorschaubild
    Publikation
    CoolShift – Cooling of buildings by chiller-assisted nocturnal radiation and convection
    (IOP Publishing, 04.09.2019) Koch, Manuel; Dott, Ralf; Eismann, Ralph; Scartezzini, Jean-Louis [in: CISBAT 2019 International Conference. Climate Resilient Cities – Energy Efficiency & Renewables in the Digital Era]
    A novel approach for cooling an office building is numerically evaluated. PVT collectors are used for nocturnal radiative and convective cooling. A TABS ceiling serves as thermal storage. If the free cooling power of the PVT collectors is too low, it is boosted by a chiller raising the collector temperature. While the energy efficiency improves compared to a conventional daytime chiller cooling system, the room temperature cannot always be kept in the desired band. Furthermore, the PVT collectors stay cooler than comparable PV modules during the day, increasing the electricity generation.
    04B - Beitrag Konferenzschrift
  • Vorschaubild
    Publikation
    CoolShift. Cooling of buildings by chiller-assisted nocturnal radiation and convection
    (IOP Publishing, 2019) Koch, Manuel; Dott, Ralf; Eismann, Ralph [in: Journal of Physics: Conference Series]
    A novel approach for cooling an office building is numerically evaluated. PVT collectors are used for nocturnal radiative and convective cooling. A TABS ceiling serves as thermal storage. If the free cooling power of the PVT collectors is too low, it is boosted by a chiller raising the collector temperature. While the energy efficiency improves compared to a conventional daytime chiller cooling system, the room temperature cannot always be kept in the desired band. Furthermore, the PVT collectors stay cooler than comparable PV modules during the day, increasing the electricity generation.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Pipe Network Analysis for Solar Thermal Plants
    (ISES Conference Proceedings, 10.09.2018) Eismann, Ralph; Haeberle, Andreas [in: EuroSun, 12th International Conference on Solar Energy for Buildings and Industry]
    Efficiency, cost-effectiveness and operational safety of solar plants must be based on the knowledge of pressure loss as well as flow distribution and temperature distribution of branched collector arrays. Therefore, pipe network analysis is an essential step during the dimensioning process. This article presents an explicit, fast converging numerical scheme especially suited for collector fields. The effect of pipe dimensions and pipe routing on flow, temperature and pressure-distribution and collector field efficiency is demonstrated by application of a dedicated software tool, which is provided as an open source code.
    04B - Beitrag Konferenzschrift
  • Vorschaubild
    Publikation
    An Explicit and Continuous Friction Factor Correlation for Helical Tubes with Arbitrary Roughness
    (Global Digital Central, 11.04.2018) Eismann, Ralph; Adams, Robert [in: Frontiers in Heat and Mass Transfer]
    Convergence of numerical schemes for pipe network analysis requires continuous modelling of pressure losses in the transition region between laminar and turbulent regions. Several existing correlations for the friction factor of straight pipes and helical tubes are presented. Based on these correlations a new explicit correlation for helical tubes with arbitrary surface roughness is derived. The friction factor is expressed as a continuous function of the Reynolds number covering laminar, transitional, and turbulent flow regions. Potential sources of error are also discussed, including the effects of tube deformation caused by the bending process.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild nicht verfügbar
    Publikation
    02 - Monographie
  • Vorschaubild nicht verfügbar
    Publikation
    Accurate analytical modeling of flat plate solar collectors: Extended correlation for convective heat loss across the air gap between absorber and cover plate
    (Elsevier, 2015) Eismann, Ralph [in: Solar Energy]
    The well-established correlation of Hollands et al. (1976), which is applicable to isothermal boundaries and Rayleigh numbers up to 105, underestimates the convective heat loss across the air gap of flat plate solar collectors with tube-and-sheet type absorbers both in normal operation and at stagnation. Two reasons for this discrepancy were identified. (1) The Rayleigh number of the air gap above absorbers with highly selective coatings can be three times as high as the application limit. (2) The absorber is not isothermal during normal operation. Based on a literature study and theoretical considerations the application limit of the correlation was extended to Ra =3 105. By means of an analytically derived correction parameter, the correlation was adapted to non-isothermal boundary conditions. For the cost- and efficiency optimization of flat-plate collectors an accurate analytical model was developed, based on the model of Duffie and Beckman (1991), enhanced by the new correlation for convective heat loss between absorber and cover plate. The model was validated against data of standardized collector tests. It is able to predict both the thermal efficiency and the stagnation temperature within the uncertainty limit of the standardized test method EN 12975-2 (CEN, 2006).
    01A - Beitrag in wissenschaftlicher Zeitschrift