Open Access

This study investigates the influence of domain definition and interface placement on the steady-state CFD prediction of performance curves of centrifugal fans. The focus is on the separation between rotating and stationary flow domains as well as on the effects of the selected interface treatment (Frozen Rotor vs. Mixing Plane). The results show that a physically consistent definition of the rotating domain—comprising the impeller and the surrounding vaneless space while the inlet nozzle and casing remain stationary — is essential for obtaining realistic total pressure predictions. Extending the rotating region into geometrically stationary components such as the inlet nozzle or volute casing introduces artificial shear work and erroneous inertial effects, resulting in increased losses and an underestimation of the pressure rise. A realistic rotor–outlet interface that spans the full axial height of the impeller exit yields markedly better efficiency predictions than an idealised, radially truncated interface that numerically acts as an extension of the impeller end-walls. For the present low-specific-speed fan, a moderate transition region within the vaneless space, corresponding to approximately 3–16 % above the impeller exit radius R₂, allows sufficient flow relaxation and leads to stable and physically consistent results. For steady-state simulations, Frozen Rotor solutions benefit from an interface distance of about 13 % above R₂, whereas Mixing Plane models provide the most robust and accurate performance predictions for interface positions around 6–7 % above R₂ in combination with a realistic interface geometry. Correct specification of wall motion, use of the SST k–ω turbulence model and appropriate near-wall resolution (y⁺ ≈ 1–3) are additional key factors for numerical consistency. Overall, the study demonstrates that careful domain definition, suitable interface placement, and a consistent numerical setup are essential prerequisites for physical fidelity and comparability of CFD-based performance curve simulations of centrifugal fans.

This paper presents a comprehensive evaluation of control strategies for a highly ener-gy-efficient plus-energy terraced housing complex equipped with photovoltaic generation, modulating ground-source heat pumps, electrical and thermal energy storage systems, and activation of building thermal mass. The study combines long-term monitoring data, annual simulations, and hardware-in-the-loop (HiL) experiments to assess modulating heat-controlled operation (HC), PV-controlled (PVC), and predictive control strategies, in-cluding simple predictive control (SPC) and model predictive control (MPC). The simula-tion results show that the baseline HC operation already achieves a high load cover factor (LCF), defined as the fraction of total electrical demand covered by local PV generation (direct use + battery discharge) of 65.6% and a seasonal performance factor (SPF) of the central heat pumps of 5.8. PVC increases LCF (71.0%) by shifting heat pump operation toward PV-rich periods but leads to elevated storage temperatures up to 5 K and a reduced SPF of 4.8. MPC further enhances LCF by 4–7 percentage points in simulated and HiL en-vironments. However, its real-world performance is strongly influenced by forecast quality and the limited controllability of the heat pump system. In addition, building thermal mass activation is investigated as a complementary flexibility option. Simulation and monitoring results demonstrate that moderate room temperature set-point (2 K) increases during PV availability significantly improve LCF from 20% to 55% while maintaining thermal comfort. Overall, the findings indicate that in highly efficient plus-energy build-ings, robust rule-based strategies combined with thermal mass activation can achieve a large share of the attainable benefits, while the added complexity of MPC must be carefully weighed against practical limitations.

Manufacturing companies have a strong impact on climate change due to their immense degree of greenhouse gas emissions. Hence, it is mandatory that these companies take measures to reduce their greenhouse gas emissions. A promising measure is the reduction of the carbon footprint caused by single processes within manufacturing process networks. Various approaches to reduce the carbon footprint of single manufacturing processes have already been described in literature. However, there is a scientific need for action when it comes to the systematic reduction of the carbon footprint of queueing systems which are typically an integral element of manufacturing process networks. Therefore, this paper presents a novel approach that aims to assess and reduce the carbon footprint of manufacturing queueing systems systematically. First, a general queueing system is defined and its variables that contribute to the carbon footprint in manufacturing are determined. Subsequently, a mathematical model is designed which enables an abstract description of the interactions of different input variables on the carbon footprint of queueing systems in manufacturing. Afterwards, recommendations to reduce the carbon footprint of queueing systems are developed based on the previous findings. Finally, the approach is validated for a specific manufacturing queueing system with a discrete-event simulation study. The results give foundations for further research on dependencies within manufacturing process networks.

Die Fakultäten Angewandte Chemie sowie Maschinenbau und Versorgungstechnik kooperieren eng in der Forschung zu Schmierfetten. Die Schwerpunkte dieser Zusammenarbeit liegen auf der Herstellung, Charakterisierung und Wirkung von Fetten. Um den Studierenden beider Fakultäten bereits im Bachelorstudium die Möglichkeit zu geben, sich mit dem Thema „Schmierfette" vertraut zu machen, ist die Einrichtung eines „virtuellen" fakultätsübergreifenden Labors geplant. In einem ersten Schritt wurden Versuche entwickelt, die es zukünftigen interdisziplinären Studierendengruppen ermöglichen, eigenständig Schmierfette herzustellen und zu prüfen. Diese fakultätsübergreifende Zusammenarbeit soll die interdisziplinären Kompetenzen der Studierenden fördern und den Zugang zu komplexen Inhalten erleichtern.