Additives Shear-Thinning and Turbulence Damping Influence on the Fitting Loss Coefficient of Bends

The flow of a drag-reducing surfactant solution in a bend with a curvature radius of 1.5 is considered, where 20 mm is the pipe inside diameter.BMWI, 03ET1197A, Energieoptimiertes Bauen (EnOB): Bionische Wärme- und Kältenetze (BioNet

Applicability of Drag Reducing Agents in Domestic Heating Systems

A special test rig was built to investigate the applicability of drag reducing agents, especially in domestic heating systems, detect problems inside the technical implementation and describe the difference between ideal characterization and application.BMWI, 03ET1197A, Energieoptimiertes Bauen (EnOB): Bionische Wärme- und Kältenetze (BioNet

Is the air change efficiency sufficient to assess the removal of airborne contamination in mixing ventilation?

This investigation analyze the correlation between two common methods to assess the ventilation effectiveness: An averaged contamination removal effectiveness (CRE) value based on the residual lifetime and the air change efficiency (ACE) to better understand their relationship to then give a recommendation for the IAQ-assessment of ventilation designs. The present numerical investigation puts focus on a simple mixing ventilation scenario with different conditions: air change rate, specific heat flux, supply air diffuser and exhaust position. Statistically, the results show a significant correlation. A detailed consideration, especially for the partial load range, will be necessary to for a valide determination of removing airborne contaminationpublishedVersio

Methodology to design district heating systems with respect to local energy potentials, CO2-emission restrictions, and federal subsidies using oemof

To combine a variety of different heat generating technologies, static design methods will not be sufficient to design future heat supply systems. New energy system design approaches are being developed with consideration of fluctuating renewable energy sources, different subsidy measures, as well as CO2-emission reduction targets. The motive of this study is to develop a new methodology to design and optimise an energy system considering these constraints. The methodology is developed based on the Open Energy Modelling Framework (oemof) and applied on a sub-urban region in northern Germany. Local specifics of energy source potentials are taken into account. It adapts the boundary conditions of a German federal funding program for innovative heat supply networks “Heating Network Systems 4.0.” Federal funding restrictions of combined heat and power systems and self-consumption are also considered. An economic optimisation was conducted considering a variety of energy sources. Cost optimal energy system design was computed regarding investments costs, energy prices and annual CO2-emission restrictions. The integration of combined heat and power (CHP), photovoltaic (PV) and heat pump (HP) systems in combination with storage size optimisation can reduce CO2-emission of heat production by approx. 69% compared to the current state of heat production

Experimental Investigation of the Spread of Airborne CFU in a Research-OR under Different Air Flow Regimes using Tracer Particles

Aim of this experimental study is to compare different types of ventilation in operating rooms (OR) regarding the highest possible patient protection against airborne germs based on particle counting. Tracer particles with the size of the airborne colony-forming units (CFU) occurring in OR shall be generated to derive representative statements about the removal of germs. In addition, they origin from aerosol generators mounted on heated person simulators to obtain a realistic dispersion of the contamination. It can be shown that the aerosol generators designed produce particles in the relevant size classes of the airborne germs emitted by OR personnel.publishedVersio

Aerosol emission in professional singing of classical music

In this study, emission rates of aerosols emitted by professional singers were measured with a laser particle counter under cleanroom conditions. The emission rates during singing varied between 753 and 6093 particles/sec with a median of 1537 particles/sec. Emission rates for singing were compared with data for breathing and speaking. Significantly higher emission rates were found for singing. The emission enhancements between singing and speaking were between 4.0 and 99.5 with a median of 17.4, largely due to higher sound pressure levels when singing. Further, significant effects of vocal loudness were found, whereas there were no significant differences between the investigated voice classifications. The present study supports the efforts to improve the risk management in cases of possible aerogenic virus transmission, especially for choir singing

Turbulence model performance for ventilation components pressure losses

This study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×10 4 and 6×10 5 , depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×10 5 . An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.BMWi, 03ET1606A, EnOB: LuftKonVerTeR - Berechnungs- und Bewertungsgrundlagen für den dynamischen Betrieb von Lüftungssystemen, bestehend aus RLT-Anlage (Konditionierung) und Kanalnetz (Verteilung) zur Steigerung der Energieeffizienz im Teillastbetrieb. Teilvorhaben: VerteilungTU Berlin, Open-Access-Mittel – 202

Algorithms for characterization and trend detection in spatial databases

The number and the size of spatial databases, e.g. for geomarketing, traffic control or environmental studies, are rapidly growing which results in an increasing need for spatial data mining. In this paper, we present new algorithms for spatial characterization and spatial trend analysis. For spatial characterization it is important that class membership of a database object is not only determined by its non-spatial attributes but also by the attributes of objects in its neighborhood. In spatial trend analysis, patterns of change of some non-spatial attributes in the neighborhood of a database object are determined. We present several algorithms for these tasks. These algorithms were implemented within a general framework for spatial data mining providing a small set of database primitives on top of a commercial spatial database management system. A performance evaluation using a real geographic database demonstrates the effectiveness of the proposed algorithms. Furthermore, we show how the algorithms can be combined to discover even more interesting spatial knowledge