Optické metody pro studium filtračních procesů na nanovlákenných filtrech
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Technická Univerzita v Liberci
Abstract
Práce se zabývá vizualizací a optickými experimentálními metodami pro studium filtračních procesů na nanovlákenných filtračních materiálech. Nanovlákenná textilie se vyznačuje velmi vysokým specifickým povrchem a malou velikostí pórů a díky těmto přednostem má výborné filtrační vlastnosti, ale v porovnání s jinými filtry disponuje horší mechanickou odolností. Cíl práce lze rozdělit na vývoj vizualizační metody pro studium filtračních procesů a na vývoj semi-kvantitativní optické metody pro hodnocení lokální účinnosti filtrace a jejího vývoje v čase. Vizualizace filtrace umožňuje neinvazivní pohled na filtrační proces v laserovém řezu. Tímto způsobem lze vizualizovat proudění v okolí filtračního materiálu a způsob dopadu částic na filtr, pozorovat desintegraci a zanášení filtrační vrstvy. Provedením obrazové analýzy lze potom kvantifikovat filtrační děj a měřit tak lokální efektivitu filtrace v čase, která souvisí se strukturálními vlastnostmi filtrů. Metoda je založena na optickém měření lokální koncentrace částic, které je v práci teoreticky rozebráno a experimentálně ověřeno. Dále je zpracována teorie rozptylu světla a měření intenzity světla digitální CCD kamerou. Byly změřeny parametry metody a provedena citlivostní analýza. Na závěr jsou uvedeny vybrané výsledky z experimentů demonstrující využití vizualizační a měřicí metody v praxi.
The thesis deals with visualization and optical experimental methods for investigation of filtration processes on nanofibrous filtration materials. A nanofibrous textile is characterized by a very high specific surface and small pore size. Thanks to this, the nanofibrous material has excellent filtration features but poor mechanical robustness compared to the other filters. The goal of the work can be divided into development of a visualization method for investigation of filtration features and into development of a semiquantitative optical method for evaluation of local filtration efficiency in time. The visualization of a filtration enables a noninvasive view on the filtration process in a laser sheet. In this way the fluid flow, the manner of particle impact on a filter, desintegration of the filter and fouling of the filter layer is possible to observe. If an image analysis of the recorded camera frames is carried out, the efficiency of the local filtration versus time can be determined, which is related to the filter morphology. The optical method is based on determination of the local concentration of particles within a laser sheet. In the thesis the theory of light scattering and the measurement on light intensity by the CCD camera was described. The relationship of the concentration of particles with a digital grey value of pixels in an image was theoretically described and experimentally verified. Parameters of the method were measured and a sensitivity analysis was carried out. Some selected experimental results were described to show the visualization and measuring method in practice.
The thesis deals with visualization and optical experimental methods for investigation of filtration processes on nanofibrous filtration materials. A nanofibrous textile is characterized by a very high specific surface and small pore size. Thanks to this, the nanofibrous material has excellent filtration features but poor mechanical robustness compared to the other filters. The goal of the work can be divided into development of a visualization method for investigation of filtration features and into development of a semiquantitative optical method for evaluation of local filtration efficiency in time. The visualization of a filtration enables a noninvasive view on the filtration process in a laser sheet. In this way the fluid flow, the manner of particle impact on a filter, desintegration of the filter and fouling of the filter layer is possible to observe. If an image analysis of the recorded camera frames is carried out, the efficiency of the local filtration versus time can be determined, which is related to the filter morphology. The optical method is based on determination of the local concentration of particles within a laser sheet. In the thesis the theory of light scattering and the measurement on light intensity by the CCD camera was described. The relationship of the concentration of particles with a digital grey value of pixels in an image was theoretically described and experimentally verified. Parameters of the method were measured and a sensitivity analysis was carried out. Some selected experimental results were described to show the visualization and measuring method in practice.
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Rozptyl světla, vizualizace proudění, filtrační proces, filtrace vody, nanovlákenné filtrační materiály, nanofiltrace, Light scattering, flow visualization, filtration process, water filtration, nanofibrous filtration materials, nanofiltration