Please use this persistent identifier to cite or link to this item: doi:10.24405/13600
Title: Neuartiges automatisiertes Schwingquarzviskosimeter mit Referenzqualität
Other Titles: New automated torsional quartz viscometer with reference quality
Authors: Junker, Clemens 
Language: ger
Keywords: Viskosimeter;Piezoelektrik;Stoffdaten;Viskosität;Toluol
Subject (DDC): 620 Ingenieurwissenschaften
Issue Date: 2021
Publisher: Universitätsbibliothek der HSU/UniBwH
Document Type: Thesis
Publisher Place: Hamburg
A viscometer has been developed for highly accurate viscosity measurements of Newtonian fluids in the temperature range between 200 K to 420 K and at pressures up to 100 MPa. The viscosity sensor is a piezoelectric quartz cylinder, which is driven by an alternating electric field to perform torsional vibrations at its resonance frequency. Measurements of the vibration are performed both in the fluid and in vacuum as the resonant frequency and bandwidth of the cylinder shift due to viscous friction of the fluid on the cylinder surface. Theses shifts and the geometrical parameters of the quartz cylinder are the measurands to obtain the product of viscosity times density of the fluid.
The measurement uncertainty of this viscometric technique has been reduced substantially below 1 %, enabling it for measurements of standard reference quality. This improvement was possible because the theory of the torsionally vibrating quartz sensor was studied in much more detail than in the past. The electric field in the viscosity sensor was analyzed mathematically for the first time with respect to various electrode configuations. This resulted in a novel sensor design where the quartz cylinder is mounted at its mid plane using thin cover slips, which were placed in notches parallel to the crystalographic axes. The quartz cylinder is surrounded by four thin stainless steel wires as electrodes, similar to a quadrupole of four line conductors. This sensor is much simpler to machine and to assemble than previous embodiments.
The purity of the torsional vibration of the anisotropic quartz cylinder was also analyzed for the first time. This lead to a more accurate working equation for the viscometer. The radius of the quartz cylinder was determined by calibration with a viscosity standard. However, if the geometry and the mass of the quartz cylinder were measured with sufficient accuracy, this viscometer could perform absolute measurements. Finally, the operation of the instrument was automated so that comprehensive measurements could be performed with toluene to validate the accuracy of the new viscometer. Comparisons with literature data underscore the superior performance of the instrument over its full pressure and temperature range.
Organization Units (connected with the publication): Thermodynamik 
Advisor: Meier, Karsten 
Referee: Wagner, Joachim
Grantor: HSU Hamburg
Type of thesis: Doctoral Thesis
Exam date: 2021-06-08
Appears in Collections:2 - Theses

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