Eismann, Ralph
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Eismann, Ralph
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- PublikationCoolShift. 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
- PublikationAn 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