NATURAL VENTILATION OF HIGH-RISE BUILDINGS - A Methodology for Planning With Different Analysis Tools and Case-Study Integration

Natural ventilation of buildings has the potential to significantly reduce energy consumption related to cooling and fanning. This can be achieved by providing good indoor air quality without any electricity demand and improving thermal comfort in the summer through increased daytime airspeed and high night ventilation rates. In high-rise buildings, however, natural ventilation is still not a widely preferred means of ventilation. The main reason is the lack of information on the required system design. Evaluation tools and instruments are not suitable for complex flow path design. Only few results are available on the performance of naturally ventilated high-rise buildings, especially where energy conservation is considered. The current thesis is predicated on this research gap. The existing barriers for implementing passive technologies can be lowered by creating a quantifiable framework that accounts for all the relevant input parameters in the design process. In order to reach this goal, a planning and simulation approach is developed. Simulations results are compared to those of a reference case-study. The 28-floor ‘Kanyon’ office tower, situated in Istanbul, is selected to demonstrate the applicability. From the energy metering, it is concluded that mechanical cooling and ventilation result in significant electricity consumption. Detailed information on the building and its operation has been made available by the building management. In addition, the impact of different moderate climates is analysed. The primary objectives of the thesis can be stated as the development of a design approach, and the investigation of the feasibility of the proposed design, based on an existing case-study building virtually adapted. The approach is developed in three steps, including conceptual design considerations, the development of a preliminary design tool, and a detailed design development. In the first step, an architectural concept is developed for wide-shaped high-rise buildings where it is impossible to realise simple cross or single-sided ventilation. Conceptual adaptations addressing the flow-path design are a central chimney strategy in respect to the building width, isolated, modular segments in respect to the building height and opposed, wind adapting openings. Other solutions proposed for passive cooling are improved shading devices and activation of the structural mass for night-time ventilation. In the second step, the originally developed ‘HighVent’ planning tool is introduced. Simple electrical circuit analogies, for both ventilation and thermal models, are found to be suitable in supporting the passive system planning. As classic design day conditions are too strict for passive system design, meaningful boundary conditions are provided. Openings can be sized automatically including an optimization process. The program first calculates the flow-path for a given airflow rate with unchanging boundary conditions. These values are then provided to the thermal module, which calculates the dynamic thermal comfort. The procedure is repeated till the system size is sufficient for passive cooling. In the third step, the annual performance is exemplarily modelled with EnergyPlus building energy simulations including airflow networks and controls. This includes the ‘HighVent’ tool preliminary design outputs, the conceptual adaptations made, and the remaining features of the as-built Kanyon building. The design approach is then further evaluated by comparing mechanical operation with an operation based on passive and hybrid control. Indicators proposed to evaluate the functionality are the energy consumption compared to that of mechanical ventilation and cooling systems, and compliance with the thermal comfort limits; additional aspects are the ventilation rates and the indoor air quality reached. Simulation results indicate that properly designed and controlled natural ventilation shows a good functionality. Control over the openings is crucial, as otherwise ventilation rates can get too high and the rooms tend to cool down too much even during summer. It is shown that the ‘Adaptive Temperature Amplifier’ control algorithm developed is very robust. Differences in climate have a varying impact. For example, in the climate of Stuttgart, further adaptations to the preliminary design are not necessary, whereas in Istanbul adaptations might be reasonable. However, to satisfy the comfort expectations in Turin, there is a necessity for adaptations or a hybrid cooling concept. That humidity values meet comfort expectations must be discussed and accepted by all project stakeholders, else hybrid operation might be a good alternative. To systematically study the possible energy conservation while maintaining thermal comfort, the energy consumption of identical buildings with different variants (passive/hybrid/active) is benchmarked against the as-built scenario. Results show that the Kanyon’s primary energy input can be reduced by approximately 30% to 40% for passive operation and by 28% to 34% for hybrid operation. This verifies the initial assumption that energy conservation of passively cooled and ventilated office spaces is significant, especially when compared to highly energy consuming state-of-the-art office towers. The results of this research work are intended, on the one hand, to support building planners in better understanding and implementing passive cooling measures and, on the other hand, to contribute to further development of sustainable building practices

Experimental entanglement distribution by separable states

The distribution of entanglement between macroscopically separated parties represents a crucial protocol for future quantum information networks. Surprisingly, it has been theoretically shown that two distant systems can be entangled by sending a third mediating system that is not entangled with either of them. Such a possibility seems to contradict the intuition that to distribute entanglement, the transmitted system always needs to be entangled with the sender. Here, we experimentally distribute entanglement by exchanging a subsystem and successfully prove that this subsystem is not entangled with either of the two parties. Our implementation relies on the preparation of a specific three-mode Gaussian state containing thermal noise that demolishes the entanglement in two of the three bipartite splittings. After transmission of a separable mode this noise can be removed by quantum interference. Our work demonstrates an unexpected variant of entanglement distribution and improves the understanding necessary to engineer multipartite quantum information networks.Comment: 9 pages, 6 figure

Ultracold Chemistry and its Reaction Kinetics

We study the reaction kinetics of chemical processes occurring in the ultracold regime and systematically investigate their dynamics. Quantum entanglement is found to play a key role in driving an ultracold reaction towards a dynamical equilibrium. In case of multiple concurrent reactions Hamiltonian chaos dominates the phase space dynamics in the mean field approximation.Comment: 15 pages, 5 figure

Local foliation of manifolds by surfaces of Willmore type

We show the existence of a local foliation of a three dimensional Riemannian manifold by critical points of the Willmore functional subject to a small area constraint around non-degenerate critical points of the scalar curvature. This adapts a method developed by Rugang Ye to construct foliations by surfaces of constant mean curvature.Comment: Minor modifications, to appear in Ann. Inst. Fourier (Grenoble

Gleichungsorientierte Modellierung der Wärme- und Stoffübertragungsprozesse in Verdunstungskühltürmen

Zur Kühlung von Prozessströmen kommen aufgrund hoher Leistungsdichten häufig Verdunstungskühltürme zum Einsatz. Um die Übertragungsfläche für Wärme und Stoff zu vergrößern, werden in diesen Kühltürmen Struktureinbauten integriert. Die Weiterentwicklung von Kühlturmeinbauten und die Untersuchung der den Kühlprozess beeinflussenden Faktoren erfolgt empirisch, was eine Vielzahl von Versuchen notwendig macht. Eine numerische Simulation des Kühlprozesses kann diese Messungen unterstützen und so helfen eine Vielzahl an Versuchen einzusparen. Des Weiteren können bei versuchsbegleitender Simulation mit einem geeigneten Modell weitere Untersuchungen durchgeführt und Erkenntnisse gewonnen werden, die bei Messungen am Versuchskühlturm verborgen bleiben. In dieser Arbeit werden zwei Ansätze der numerischen Simulation eines Verdunstungskühlturms betrachtet. Es werden eine CFD-Simulation und ein vereinfachtes Modellkonzept hinsichtlich der Anwendbarkeit auf diese Problemstellung untersucht. Schwerpunkt der vorliegenden Arbeit ist die methodische Entwicklung eines solchen vereinfachten mathematischen Modells. Dieses beruht auf der physikalisch deterministischen Beschreibung der im Kühlturm ablaufenden Prozesse der Wärme- und Stoffübertragung unter Berücksichtigung des Stoffverhaltens. Aufgrund der Nichtlinearität des Stoffverhaltens und der erforderlichen Inkrementierung des Berechnungsgebiets ist ein methodisches Vorgehen erforderlich, um die Erstellung der Modellgleichungen und deren Lösung überhaupt realisieren zu können. Hierfür wird auf allgemeine Methoden der gleichungsorientierten Simulation technischer Systeme zurückgegriffen. Das entwickelte Modellkonzept wird für die Modellierung und Simulation eines Versuchskühlturms angewandt. Mit den so ermittelten Messdaten wird das Modell kalibriert und validiert. Es zeigt sich, dass mit dem erstellten Modell quantitativ und qualitativ valide Ergebnisse erzielt werden können.Due to the high power density, the cooling of process streams is often done bei evaporative cooling towers. To enlarge the exchange area for the heat and mass transfer, these cooling towers contain integrated structural fills. The future development of cooling tower fills and the research regarding the cooling process and its influencing parameters will be carried out empirically, resulting in a large number of required experiments. A numeric simulation of the cooling process can support theses measurements and reduce the vast number of needed experiments. Furthermore, with the use of test-related simulations and adapted models, it will be possible to gain knowledge and do research in areas which are omitted during regular measurements on cooling towers. In this study it is looked to two different approaches of numeric simulation of a evaporative cooling tower. There will be an examination of a CFD-Simulation and a simplified model concept regarding their respective applicability for this problem. This work is focussed on the systematic developement of such simplified mathematical models, based on the physical deterministic description of the occurring processes of heat and mass transfer in cooling towers considering the stock behaviour. Due to the non-linearity of the stock behaviour and the required incrementation of the calculation area, a systematic approach is needed to model equations and their respective solutions. For this purpose it is necessary to access general techniques of equation-based simulations of technological systems. The developed model concept will be applied for the modelation and simulation of an experimental cooling tower. The model will be calibrated and validated with data from this experimental tower. It shows, that the results from this model are qualitatively and quantitatevily valid

Structure and function analysis of two channel forming membrane proteins of medical importance – The lysosomal Transmembrane Protein 175 and the Envelope Protein of SARS-CoV-2

In this work, two channel proteins of medical importance were electrophysiologically investigated and characterized. In the first part of this work, the lysosomal TMEM175 channel was in the focus of the studies. TMEM175 is associated with the development of Parkinson’s disease (PD) through a yet unknown mechanism, underscoring the importance of this channel to regulation of cellular homeostasis. The family of TMEM175 proteins in general constitutes a recently discovered type of K+ channels that are important for autophagosome turnover and lysosomal pH regulation. From a structural point of view, TMEM175 channels lack the typical P-loop type selectivity filter, a hallmark of all canonical K+ channels. This raises the question on how K+ selectivity is achieved in TMEM175 channels. In this study, new insights gained by the X-ray structure of a closed bacterial TMEM175 channel are used in combination with electrophysiological methods to address this very question. By performing mutational studies and subsequent electrophysiological investigations, Thr38 of MtTMEM175 as well as the corresponding layer of threonines in the human homolog (hTMEM175) were found to play a pivotal role in K+ selectivity. The data suggests this mechanism to be a general explanation for K+ selectivity in TMEM175 channels. An additional layer in the hTMEM175 comprising two serines further increases selectivity and renders this channel sensitive to blockers like 4-aminopyridine and Zn2+. The combination of structural data, mutations and electrophysiological measurements indicate that large hydrophobic side chains occlude the pore, forming a physical gate in TMEM175 channels. Channel opening of MtTMEM175 by an iris-like motion simultaneously relocates the gate and exposes the otherwise concealed selectivity filter to the pore lumen. Close scrutiny of closed- and open-state hTMEM175 cryo-EM structures furthermore provides a coherent hypothesis on a gating mechanism based on charged residues at the extracellular pore entrance. In the second part of this work, the envelope protein of SARS-CoV-2 and its effects on the homeostasis of the host cell of the virus were studied. SARS-CoV-2 produces in host cells large amounts of envelope proteins (Ep-CoV-2). To mimic its pathophysiological impact, Ep-CoV-2 was expressed in mammalian cells and the effects on signaling parameters monitored. We detected fluorescent tagged Ep-CoV-2 in the endoplasmic reticulum and trace amounts in the plasma membrane. Wild-type (wt) Ep-CoV-2 and, to a lesser extent, its mutants (N15A, V25F) and the isolated transmembrane domains corrupted major signaling cascades in cells causing elevated intracellular Ca2+ as well as pH and membrane depolarization. These Ep-CoV-2-triggered effects, which potentially contribute to the pathogenesis of the viral protein, seem to result from an ion-channel activity. Two independent assays, functional reconstitution of Ep-CoV-2 in artificial membranes and rescue of K+-deficient yeast mutants, confirm that Ep-CoV-2 generates a cation-conducting channel with a low unitary conductance and a complex ion selectivity. All results together suggest that inhibitors of this channel function can provide cell protection and virostatic effects