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In Messungen bei Rettig ICC wurde beobachtet, dass gültige normative Zusammenhänge zur Auslegung von Heizkörpern und Heizflächen keine uneingeschränkte Gültigkeit mehr besitzen, wenn niedrige Auslegungs-Rücklauftemperaturen und damit größere Temperaturspreizungen die Wassermasseströme in den Heizkörpern reduzieren. Die Bestimmung der Heizleistung von Heizkörpern kann in diesem Fall möglicherweise nicht mehr zuverlässig erfolgen. Die physikalischen Begründungen für die beobachteten Phänomene werden nunmehr offengelegt und sollen der Anregung für die weitere fachliche Diskussion dienen.

Deckenstrahlplatten stellen in Großräumen ein typisches System zur Wärmeübergabe dar. Das wasserbasierte System ist hierbei an ein hydraulisches Verteilsystem angeschlossen und kann mit unterschiedlichen Erzeugungssystemen betrieben werden. Für Wärmeerzeuger (Brennwertgeräte/KWK-Systeme oder Wärmepumpen) liegen umfangreiche, energetische Untersuchungen unter verschiedensten Randbedingungen vor. Auf der Wärmeübergabeseite, zu denen Deckenstrahlplatten gehören, sind die Analysen derzeit jedoch begrenzt. Die nachfolgende Veröffentlichung fokussiert auf den Aspekt der Wärmeübergabe und stellt in ihrem Teil neue energetische Erkenntnisse im Bereich der Deckenstrahlplatten vor (Teil 1 ist erschienen in HLH Bd. 71 (2021), Nr. 9).

Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) is a promising approach with a high optimization potential for the treatment of peritoneal carcinomatosis. To study the efficacy of PIPAC and drugs, first rodent cancer models were developed. But inefficient drug aerosol supply and knowledge gaps concerning spatial drug distribution can limit the results based on such models. To study drug aerosol supply/deposition, computed tomography scans of a rat capnoperitoneum were used to deduce a virtual and a physical phantom of the rat capnoperitoneum (RCP). RCP qualification was performed for a specific PIPAC method, where the capnoperitoneum is continuously purged by the drug aerosol. In this context, also in-silico analyses by computational fluid dynamic modelling were conducted on the virtual RCP. The physical RCP was used for ex-vivo granulometric analyses concerning drug deposition. Results of RCP qualification show that aerosol deposition in a continuous purged rat capnoperitoneum depends strongly on the position of the inlet and outlet port. Moreover, it could be shown that the droplet size and charge condition of the drug aerosol define the deposition efficiency. In summary, the developed virtual and physical RCP enables detailed in-silico and ex-vivo analyses on drug supply/deposition in rodents.

The lack of data for inhalation exposure concerning the handling of nanostructured materials is limiting the current nanomaterial risk assessment. However, there are numerous studies dealing with the origin of exposure, i.e., the release. The link between release and exposure are transport and transformation phenomena. Thus, propagation modeling was used to simulate transport from source to breathing zone in order to estimate quantitative exposure levels from measured release data for selected scenarios. On the basis of three ventilation and five release scenarios, exposure levels were calculated with and without human thermal plumes for both the nearfield and the farfield. Results show that the often neglected human-induced convective airflow can have a strong impact on the level of exposure, especially for natural ventilation or non-well-designed technical ventilation systems as typical for nonindustrial consumers or handicraft businesses.

The efficient use of energy for heating and cooling of indoor environments requires an accurate prediction and analysis of radiative heat transfer. Therefore it is necessary to use modern computer methods as otherwise the computational costs may become higher than for convective heat transfer, which is known to be a huge computational problem. A key problem in calculations of radiative heat transfer is the problem of mutual visibility arising in the determination of view factors. This is the same challenge that global illumination has to cope with which is one of the fundamental topics in computational graphics. The visibility problem is efficiently solved by modern graphics hardware. Therefore an OpenGL-based algorithm is developed to quickly and accurately calculate view factors for arbitrary, complex geometries. Theoretical and implementation details of the applied methods are given. We demonstrate the advantages of the developed computational method by a virtual test room for a tubular radiator, a heating of a warehouse by ceramic infrared heaters and the heat transfer in a car cabin.

Im Zuge der hier vorliegenden Studie wurden umfangreiche numerische Untersuchungen verschiedener Klimatisierungskonzepte fur ein typisches Passivhausburo durchgefuhrt. Dabei standen sowohl energetische Aspekte als auch Aspekte des erzielbaren thermischen und hygienischen Komforts im Fokus der Betrachtungen. Die Untersuchungen erfolgten mittels gekoppelter Gebaude-, Anlagen- und Stromungssimulation und erstreckten sich uber eine Vielzahl zentraler und dezentraler Heiz-, Kuhl-, Verschattungs- und Beluftungssysteme und deren Kombinationen. Die Resultate der Untersuchungen verdeutlichen, dass auch fur Burogebaude mit ihren spezifischen Nutzungsmerkmalen, wie der hoheren Belegungsdichte und erhohter interner thermischer Lasten (gegenuber Wohngebauden) eine Bauweise im Passivhausstandard empfehlenswert ist. Bezuglich der Klimatisierungsvarianten zeigte sich zudem, dass eine Trennung von Beluftung und Temperierung (z. B. uber Heiz-/Kuhldecken) bei gleichzeitiger bodennaher Einbringung der Zuluft im Sinne des Quellluftprinzips den besten Kompromiss bezuglich Energieeffizienz und Behaglichkeit darstellt. Coupled heating, cooling and ventilation simulation with CFD for thermal comfort in a passive house standard office building. In the course of this study extensive numerical investigations of different heating, ventilation and cooling concepts were carried out for a typical passive house office. As well the energetic aspects as the thermal and hygienic comfort were taken into account. The investigations were performed by building and system simulation coupled to computational fluid dynamics (CFD). A big variety of centralized and decentralized heating, cooling, ventilation and sun screen systems and their combinations were analyzed. The results clearly show that also for office buildings with their specific feature of usage as dense occupancy and high internal loads the construction form as a passive house is advisable. In terms of heating, cooling and ventilation it was shown that a separation of ventilation and temperature regulation (e.g. by heating or cooling ceilings) with simultaneous air supply close to the floor (displacement ventilation) seems to be the best compromise between energy efficiency and thermal comfort.

Der Beitrag stellt ein im Rahmen eines Forschungsprojektes erprobtes Simulationswerkzeug vor, mit dessen Hilfe die raumklimatischen Verhältnisse in Museumsbauten nachgebildet und berechnet werden können. Die Simulationsergebnisse sind in Varianten (Sommer/Winter; Quell-/Schlitzlüftung; mit/ohne Oberlicht; Heizkörper/Temperierung nach Grosseschmidt) auswertbar - hinsichtlich der charakteristischen Kenngrößen wie z.B. Oberflächen- und Lufttemperatur, Luftaustausch/Luftqualität, Raumluftfeuchte, Zugbelastung. Diese Metadaten wurden zur Verfügung gestellt von der Literaturdatenbank RSWB®plus

Moderne Gebaude- und Raumkonzepte verlangen oft ein Umdenken gegenuber herkommlichen Losungen zur Heizung oder auch Kuhlung der Gebaude. Oft ist jedoch nicht quantifizierbar, ob neue Ideen wirklich umsetzbar sind, da vereinfachte Abschatzungen eine zu grose Unscharfe besitzen. Deshalb wurde ein von den Autoren masgeblich entwickeltes und erfolgreich eingesetztes Programmsystem zur gekoppelten Gebaude-, Anlagen- und Raumluftstromungssimulation mit einem weiteren raumlich und zeitlich hoch aufgelosten Modell fur die Heiz- und Kuhlkorpersimulation gekoppelt. Auf diese Weise konnen nicht nur Prufszenarien aus der Heizungstechnik nachgebildet, sondern auch spezielle Betriebsverhaltnisse oder Kuhlkorper zur Raumtemperierung untersucht werden. Die Ansatze fur die Modellierung sind kurz erlautert, ausgewahlte Ergebnisse werden vorgestellt und diskutiert (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Combined thermal building simulation for advanced heating and cooling specification. Modern concepts of buildings and rooms require a rethinking concerning conventional solutions for heating or cooling of buildings. But often it is not possible to quantify, whether a new idea is worthwhile because of missing sharpness of simple assessments. Therefore a programming system for combined thermal building simulation and indoor air flow calculation, mainly developed and successfully applied by the authors is extended by a highly resolved model for heating and cooling devices. In that way it is possible to model the specification of radiators in a test chamber or under operating conditions. In addition, the effect of cooling by radiators can be investigated. The approaches for modelling will be explained in short and some selected results are presented and discussed.

Die rechnerische Vorhersage naturlicher Luftungsvorgange in Gebauden gestaltet sich aufgrund der Problematik der Randbedingungen und der instationaren Natur des Vorganges oft schwierig. Hinzu kommt, das der reine Luftungsvorgang lediglich eine Teil information liefert, wenn beispielsweise Nachtluftungen und die damit einhergehende Entwarmung untersucht werden mussen. Unter Nutzung der Moglichkeiten einer speziellen Finite-Elemente-Methode (FEM) lassen sich Randbedingungsformulierungen finden, die fur die Berechnung naturlicher Luftungsvorgange geeignet sind. Weiterhin werden Moglichkeiten und Kriterien vorgestellt, instationare Luftungsvorgange unter hygienischen und energetischen Gesichtspunkten zu analysieren. Der energetische Aspekt lasst sich besonders herausarbeiten, wenn man Raumluftstromungsberechnung und thermische Gebaudesimulation geeignet kombiniert. Prediction and analysis of natural ventilation. The computational prediction of natural ventilation is often raising difficulties because of problematic boundary conditions and the unsteady nature of the flow. In addition, the pure ventilation process only delivers a part of information, for instance in case of night ventilation for cooling purposes. Using the possibilities of a special stabilized FEM-code one is able to find formulations for boundary conditions, which are very useful for the simulation of natural ventilation problems. Furthermore we present some criteria and possibilities for the analysis of transient ventilation tasks from the energetic and the hygienic point of view. By combining indoor air flow computation and thermal building simulation the energetic consideration can be especially performed.

We present a fully parallelized, high-performance, OpenGL-based approach to compute obstructed area-to-area (A2A) view factors for radiative heat transfer. The A2A view factors are computed from the defining surface integral by Gaussian quadrature. The values of the integrand, i.e. the point-to-area view factors, are computed using an OpenGL-based hemicube (HC) method to efficiently solve the obstruction problem by exploiting the hardware-accelerated visibility testing on modern graphics cards. The final steps to maximize hardware usage are rendering the HC and performing the numerical quadrature in parallel such that data transfer times are completely shadowed by computations. To demonstrate the power of our approach we compute the A2A view factor matrices for a warehouse equipped with ceramic infrared heaters and a test cabin conforming to EN 442 containing a section of a panel radiator. To judge the quality of the results we measure the deviation from unity of the area-weighted column sums of the view factor matrix and the error in radiant flux balance. Compared to a previous, ray-tracing-based implementation, we gain three orders of magnitude in speed in the view factor computation. Conservation of radiant flux is also substantially improved.

We consider the numerical simulation of buoyancy-affected, incompressible turbulent flows using a stabilized finite-element method. We present an approach which combines two domain decomposition methods (DDM). Firstly, we apply a DDM with full overlap for near-wall modelling, which can be interpreted as an improved wall-function concept. Secondly, a non-overlapping DDM of iteration-by-subdomains-type for the parallel solution of the linearized problems is employed. For this scheme, we demonstrate both the accuracy for a benchmark problem and the applicability to realistic indoor-air flow problems.

The parallel solution of the incompressible Navier–Stokes equations coupled with the energy equation is considered. For turbulent flows, the k/e model together with a modified wall-function concept is used. The iterative process requires the fast solution of advection–diffusion reaction and Oseen-type problems. These linearized problems are discretized using stabilized finite element methods. We apply a coarse–granular iterative substructuring method which couples the subdomain problems via Robin-type interface conditions. Then we apply the approach to the simulation of indoor air flow problems. Copyright © 2002 John Wiley & Sons, Ltd.

The gap between release and exposure is limiting the current risk assessment of nanostructured materials. Both, release and exposure were connected to each other by transport and transformation processes and require therefore the description/specification of complex exposure scenarios. Within this study, propagation modelling based on experimentally determined airborne particle release data was used for exposure estimation and prediction in a defined model room. Therefore, 9 different exposure scenarios based on 3 release scenarios and 3 ventilation scenarios were analysed. Results for near field considerations have shown that the level of inhalation exposure is fundamentally defined by the present exposure scenario, that personal heat can cause particle availability in the breathing zone and that highest exposure levels arise immediate during material processing.

The non-isothermal, incompressible Navier-Stokes equations with Boussinesq approximation are considered as a model of turbulent indoor air flows. The transient calculation is based on the Reynolds-averaged Navier-Stokes problem using the k/e-turbulence model or improved variants such as the ν 2 -f model. The model is first discretized in time using backward-differencing schemes and then linearized using a Newton-type method per time step with emphasis on the proper calculation of (non-negative) turbulence quantities. The resulting auxiliary problems of Oseen type and of advection-diffusion-reaction type are solved using stabilized finite element method of residual type. Here we summarize some of our recent analytical results for higher-order methods and shock-capturing techniques. The numerical solution to the model in boundary layer regions is obtained using either adaptive wall functions if the k-s model is used or a hybrid mesh with anisotropic refinement if the ν 2 -f model is applied. Besides the standard flow quantities, it is possible to calculate quantities such as the age of the air. Such quantities are used to develop criteria for the evaluation of the efficiency of air exchange in a room. The Quality of the numerical simulations is demonstrated for typical benchmark problems.

A framework for solving the non-isothermal unsteady Reynolds-averaged Navier-Stokes equations with emphasis on applications to thermal building simulation is prescribed in this paper. Different domain decomposition techniques are used (i) for the treatment of boundary layers, (ii) for the efficient solution of the arising linear subproblems, and (iii) for coupling the indoor air flow field with the ambient. The approach is then applied to exemplary indoor air flow configurations.

Nonstationary incompressible flow problems can be split into auxiliary problems of Oseen type. We present the analysis of conforming stabilized Galerkin methods of SUPG/PSPG-type with equal-order interpolation of velocity/pressure and with emphasis on anisotropic mesh refinement in boundary layers. We prove a modified inf-sup condition with a constant independent of the viscosity and of critical parameters of the mesh. Numerical tests confirm the results.