Thermodynamic studies in flow metrology

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Insinööritieteiden ja arkkitehtuurin tiedekunta | Doctoral thesis (article-based)
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Date
2009
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Language
en
Pages
Verkkokirja (804 KB, 82 s.)
Series
Publication /Mikes. 13/2008
Abstract
Thermodynamic studies in flow metrology were carried out to improve the realization of fluid flow quantities. First, a metrological competence study of the dynamic gravimetric gas mass flow rate measurement standard of MIKES was carried out. Then, a theoretical and experimental study to clarify the varying shear stress on the cylindrical surfaces and its contribution to the combined standard uncertainty of a dynamic gravimetric gas mass flow rate standard was presented. A new mixing method for establishing a traceability link between air velocity standard and national standards of mass and time was developed. The method for compensating the effect of vertical density gradients in a liquid sample to the reading of a hydrometer was developed. In the dynamic gravimetric gas mass flow rate measurement method, the varying shear stress on the wall of the gas cylinder was studied by time averaging the instantaneous shear stress, calculated from the numerical similarity solution of laminar boundary layer equations. The model was studied experimentally by a balance combined with temperature measurements. The most commonly used primary standard in air velocity measurements is based on laser anemometry enabling the traceability to the SI base units of length and time. In this study, an alternative method of establishing the traceability link was developed. The method is based on humidification of air in the wind tunnel with the known mass flow rate of water. The air velocity can then be expressed as a function of humidification water mass flow rate enabling the traceability to the SI base units of mass and time. The method was studied in the wind tunnel of MIKES with a Pitot tube. The non-homogeneous vertical temperature distribution in the liquid sample causes errors in the reading of a hydrometer. In this thesis, a mathematical model for compensating for the effect of temperature gradients has been presented. The model was studied experimentally in the hydrometer calibration system at MIKES. The compensation model improves, for example, the accuracy of conversion between the mass and volume flow rate units. The methods presented in this thesis can be applied to improve the accuracy of primary standards for small gas flow meters and hydrometers. The mixing method provides a novel and less expensive way to establish the traceability link for air velocity measurements.
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Keywords
flow metrology, thermodynamics, gas mass flow rate, air velocity, liquid density
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Parts
  • [Publication 1]: S. Sillanpää, B. Niederhauser, and M. Heinonen. 2006. Comparison of the primary low gas flow standards between MIKES and METAS. Measurement, volume 39, number 1, pages 26-33. © 2006 Elsevier Science. By permission.
  • [Publication 2]: S. Sillanpää and M. Heinonen. 2007. The varying effect of natural convection on shear stress rate on cylindrical surfaces. Experimental Thermal and Fluid Science, volume 32, number 2, pages 459-466. © 2007 Elsevier Science. By permission.
  • [Publication 3]: Sampo Sillanpää and Martti Heinonen. 2008. The contribution of varying shear stress to the uncertainty in gravimetric gas mass flow measurements. Metrologia, volume 45, number 2, pages 249-255. © 2008 Institute of Physics Publishing. By permission.
  • [Publication 4]: S. Sillanpää and M. Heinonen. 2008. A mixing method for traceable air velocity measurements. Measurement Science and Technology, volume 19, number 8, 085409. © 2008 Institute of Physics Publishing. By permission.
  • [Publication 5]: Martti Heinonen and Sampo Sillanpää. 2003. The effect of density gradients on hydrometers. Measurement Science and Technology, volume 14, number 5, pages 625-628. © 2003 Institute of Physics Publishing. By permission.
  • [Errata file]: Errata of publications 1 and 4
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