Münster University of Applied Sciences

About: Münster University of Applied Sciences is a education organization based out in Münster, Germany. It is known for research contribution in the topics: Luminescence & Laser. The organization has 694 authors who have published 1067 publications receiving 12597 citations.

Boiling Under Hele-Shaw Flow Conditions: The Occurrence of Viscous Fingering

Abstract: Boiling and bubble dynamics were experimentally investigated in a Hele-Shaw flow cell using pure water at atmospheric pressure as working fluid. The resulting vapor bubble shapes were recorded by means of a high-speed camera for several plate spacings and heating power levels. It was found that viscous fingering phenomena of vapor bubbles occurred only under very special boiling conditions and cell parameters. The evaporation front velocity was identified as a major parameter for the onset of viscous fingering. The observed basic viscous fingering dynamics was in reasonable agreement with theoretical analyses. In addition to that classical viscous large fingering, small-scale evaporation instability was observed leading to microscopic roughening of accelerating evaporation fronts. This instability might be explicitly related to evaporative heat and mass transfer effects across the fast-moving phase interface.Copyright © 2013 by ASME

Numerical Calibration of 3D Printed Five-Hole Probes for the Transonic Flow Regime

Abstract: This paper presents a method for a cost- and time-effective calibration procedure for five-hole probes for the transonic flow regime based on additive manufacturing and a numerical calibration routine. The computational setup and calibration routine are described in detail. The calibration procedure is tested on a custom-built L-shaped conical probe of 30° half-angle with a flat tip and an outer diameter of 2.4mm. The probe tip is manufactured in stainless steel using DMLS. Numerical calibration is carried out over a Mach number range of 0.2 to 1.4 and pitch and yaw angles of ±45°. The numerical calibration charts are validated with wind tunnel tests and the expected accuracy of the numerical calibration method is quantified. Exemplary results of area traverses up- and downstream of a linear transonic turbine cascade with tip clearance are presented and discussed briefly.

Na3GaF6 - A Crystal Chemical and Solid State NMR Spectroscopic Study

Abstract: Na3GaF6 and Na3GaF6:Mn4+ samples were obtained from NaNO3 and Ga(NO3)(3)center dot 9H(2)O in hydrofluoric acid using K2MnF6 or NaMnO4 as manganese sources. The structure of Na3GaF6 was studied by single crystal X-ray diffraction at 90, 293, 440 and 500 K, confirming the monoclinic cryolite type structure, space group P2(1)/c. The gallium atoms show slightly distorted octahedral coordination by fluorine atoms, similar to the Nal atoms. Coordination number 8 is observed for Na2. Both sodium sites are clearly distinguished by Na-23 MAS-NMR spectroscopy. Above 400 K the spectra reveal distinct chemical exchange effects, signifying sodium ion hopping between these two sites. At the same time static F-19 NMR spectra indicate pronounced motional narrowing effects in this temperature region. The nearly invariant Ga-69 MAS-NMR spectra suggest that any reorientational motion involving the GaF63- ions (if present) occurs with preservation of the center of mass of these octahedra.

Method for the identification of plastics

Abstract: The invention relates to a method for identifying plastics by doping a plastic with metals or metal derivatives, processing the plastic into a molded article, and quantitatively analyzing the introduced metals or metal derivatives by means of an analytical process that allows solid sample material to be measured. The invention further relates to a standard kit for calibrating an analytical device that can be used in said methods. The inventive standard set comprises at least two calibration standards, each of which contains a molded plastic article which is doped with at least one metal selected among La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Sc, Ir, Pt, Rh, Au, Os, and V.