CFD-Simulation zur Untersuchung des Strömungsverhaltens in Strukturrohren

Die CFD (Computational Fluid Dynamics)-Simulation hat mittlerweile in alle technischen Bereiche Einzug gehalten, in denen die Vorhersage strömungstechnischer Ereignisse relevant ist. Nach wie vor ist allerdings eine Validierung von Rechenergebnissen mit Messdaten unerlässlich, um zu vertrauenswürdigen Simulationsergebnissen zu kommen. Dies ist u. a. darauf zurückzuführen, dass die am Markt verfügbare CFD-Software darauf ausgerichtet ist, ein möglichst breites Anwendungsspektrum zu bedienen. Die implementierten Berechnungsmodelle müssen im Rahmen der Modellierung durch die Wahl geeigneter Randbedingungen an den zu untersuchenden Anwendungsfall angepasst werden

Entwicklung und Leistungsbestimmung einer 2,2 kW Tesla Turbine

Im Folgenden wird die Entwicklung und Evaluation eines 2,2 kW Tesla Turbinen Prototyps beschrieben. Ausgehend von der konstruktiven Verbesserung der Ein- und Auslassströmung – mit dem Ziel der Steigerung des isentropen Wirkungsgrades – wurde ein Turbinenprototyp gefertigt und auf einem Turbinenversuchsstand erprobt. Hierbei wurde untersucht, ob eine Wirkungsgradsteigerung mit einem Profileinsatz möglich ist. Die gewonnenen Ergebnisse lagen im Erwartungsbereich und zeigten, dass der Profileinsatz zu einer Wirkungsgradsteigerung bei beiträgt.This article deals with the development and evaluation of a 2.2 kW Tesla Turbine prototype. Based on design improvements of the in- and outflow of the turbine, with the goal of increasing the isentropic efficiency, a Tesla Turbine Prototype has been built and tested in a turbine test rack. It was investigated whether a profiled shaft inset can increase the isentropic efficiency of the turbine. The results were achieved and demonstrated that a profiled shaft can increase the efficiency of the turbine

The Simulation of Convective Heat Transfer in a Tesla Turbine Gap

Due to its unique design and large rotor surface, the Tesla turbine is predestined for heat transfer processes. To calculate the heat transfer, a simple steady state model based on the Blasius boundary layer analogy was developed and compared to a numerical simulation. It could have been shown, that the model fits the numerical simulation well for the surface heat flux and the Nusselt number. For the heat transfer coefficient, the simplified model needs a refinement due to a different calculation approach between the numerical simulation and the analytic solution. Furthermore, it could be shown, that the simplified model can only be applied if the turbine inlet velocity is in the range of the disk velocity. Otherwise a flow channel develops which is not covered by the simplified model

Optimization of porous materials for thermochemical storage of heat

Increasing interest in the application of the thermochemical storage or adsorption heat pumps for utilization of industrial waste heat and solar heat stimulated several experimental and theoretical studies on short and long term heat storage (Tchernev, 2001, Mittelbach et al., 2000, Hauer et al.,1999) as well as heat driven heat pumps (Meunier,, 1986, Dieng, and Wang, 2001). However, less attention was paid to the properties of the porous materials such as common zeolites, silica gels or aluminosilicates which are mainly designed for catalysis and adsorption technologies but are not optimized for thermochemical heat storage applications. In recent years some new storage materials were suggested and characterized such as the so called composite adsorbens (Levitskij et al., 1996, Jänchen et al., 2000) which have considerable high storage densities, a low charging temperature but their temperature lift is limited. Very recently (Jänchen, et al., 2002) we suggested the introduction of the AlPO4’s for heat storage and heat transformation purposes. AlPO4’s are zeolites-like microporous materials, which are mildly hydrophilic and may have the potential to close the gap between silica gels and zeolites in respect to the optimization of the adsorption strength of the water and the ability to be desorbed at mild conditions. Those microporous aluminophosphates can be modified by incorporation of some silicon into the lattice to tailor their adsorption properties with respect to the water adsorption/desorption properties. The aim of this paper is to characterize the state of the art of the optimization of those new thermochemical storage materials, based on recent results, as an starting point for a continuation of the this project

Preparation, hydrothermal stability and thermal adsorption storage properties of binderless zeolite beads

Abstract Novel binderless zeolite beads of types A and X have been synthesized and characterized by scanning electron microscopy, mercury intrusion, nitrogen adsorption, thermogravimetry, water adsorption isotherm measurements, cyclic hydrothermal treatments and storage tests. The binderless molecular sieves show an improved adsorption capacity, sufficient hydrothermal stability, higher specific energies and the potential for a better performance density of the storage. Both open and closed storage tests have shown comparable adsorption capacities and specific energies for the binderless molecular sieves. A significantly higher discharging temperature, however, could be realized with the open storage system

Predictive Value of Multiparametric MRI for Response to Single-Cycle Induction Chemo-Immunotherapy in Locally Advanced Head and Neck Squamous Cell Carcinoma

Objectives To assess the predictive value of multiparametric MRI for treatment response evaluation of induction chemo-immunotherapy in locally advanced head and neck squamous cell carcinoma. Methods Twenty-two patients with locally advanced, histologically confirmed head and neck squamous cell carcinoma who were enrolled in the prospective multicenter phase II CheckRad-CD8 trial were included in the current analysis. In this unplanned secondary single-center analysis, all patients who received contrast-enhanced MRI at baseline and in week 4 after single-cycle induction therapy with cisplatin/docetaxel combined with the immune checkpoint inhibitors tremelimumab and durvalumab were included. In week 4, endoscopy with representative re-biopsy was performed to assess tumor response. All lesions were segmented in the baseline and restaging multiparametric MRI, including the primary tumor and lymph node metastases. The volume of interest of the respective lesions was volumetrically measured, and time-resolved mean intensities of the golden-angle radial sparse parallel-volume-interpolated gradient-echo perfusion (GRASP-VIBE) sequence were extracted. Additional quantitative parameters including the T1 ratio, short-TI inversion recovery ratio, apparent diffusion coefficient, and dynamic contrast-enhanced (DCE) values were measured. A model based on parallel random forests incorporating the MRI parameters from the baseline MRI was used to predict tumor response to therapy. Receiver operating characteristic (ROC) curves were used to evaluate the prognostic performance. Results Fifteen patients (68.2%) showed pathologic complete response in the re-biopsy, while seven patients had a residual tumor (31.8%). In all patients, the MRI-based primary tumor volume was significantly lower after treatment. The baseline DCE parameters of time to peak and wash-out were significantly different between the pathologic complete response group and the residual tumor group (p < 0.05). The developed model, based on parallel random forests and DCE parameters, was able to predict therapy response with a sensitivity of 78.7% (95% CI 71.24–84.93) and a specificity of 78.6% (95% CI 67.13–87.48). The model had an area under the ROC curve of 0.866 (95% CI 0.819–0.914). Conclusions DCE parameters indicated treatment response at follow-up, and a random forest machine learning algorithm based on DCE parameters was able to predict treatment response to induction chemo-immunotherapy

The IceCube Neutrino Observatory, the Pierre Auger Observatory and the Telescope Array: Joint Contribution to the 34th International Cosmic Ray Conference (ICRC 2015)

We have conducted three searches for correlations between ultra-high energy cosmic rays detected by the Telescope Array and the Pierre Auger Observatory, and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses with UHECRs are done: one with 39 cascades from the IceCube `high-energy starting events' sample and the other with 16 high-energy `track events'. The angular separation between the arrival directions of neutrinos and UHECRs is scanned over. The same events are also used in a separate search using a maximum likelihood approach, after the neutrino arrival directions are stacked. To estimate the significance we assume UHECR magnetic deflections to be inversely proportional to their energy, with values $3^\circ$, $6^\circ$ and $9^\circ$ at 100 EeV to allow for the uncertainties on the magnetic field strength and UHECR charge. A similar analysis is performed on stacked UHECR arrival directions and the IceCube sample of through-going muon track events which were optimized for neutrino point-source searches.Comment: one proceeding, the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands; will appear in PoS(ICRC2015