| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 107 === The draining vessel method is used to simultaneously measure density, viscosity and surface tension coefficient of fluid. This study propose using CFD instead of the modified formulation to improve the accuracy of results. In the draining vessel, the drag force caused by viscosity and surface tension balancing the draining force by gravity. The fluid elevation head and the mass flux of the flow through the orifice at the vessel bottom reveal the influence quantitatively by the physical properties of viscosity, surface tension and fluid density. A nonlinear and multi-variable regression is used to calculate the values of fluid properties by minimizing the difference between the elevation head gained from simulation and experiment.
The obtained results for water at 299K show the physical properties were measured with the percentage error of -1.77 % in density, -5 % in viscosity and -30.42 % in surface tension coefficient compared to the values quoted from literature. In addition, results for ethylene glycol also yield percentage errors of 4.95 %, 11.98 %, and 34.02 % in density, viscosity and surface tension coefficient, respectively. According to the error analysis, the uncertainty of the size of device and computational error may be responsible for the calculation error of the fluid properties. While the accuracy exhibited by the results is high, it can be further enhanced by decreasing the uncertainties as mentioned above, this method could be extended for use in various applications and become a relatively affordable option.
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