Browsing by Author "Wang, Yan"

Now showing 1 - 12 of 12
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    A novel method for producing bi-component thermo-regulating alginate fiber from phase change material microemulsion
    (SAGE PUBLICATIONS LTD, 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND, 2019-11-01) Wang, Yan; Yao, Juming; Zhu, Guocheng; Militký, Jiří; Marek, Jaromír; Venkataraman, Mohanapriya; Zhang, Guoqing
    A novel method for fabricating thermo-regulating alginate fiber by wet spinning from phase change material (PCM) microemulsions was proposed and carried out. In order to synthesize the PCM microemulsion successfully, different emulsifiers (alkylphenol polyoxyethylene ether (OP-10), sodium dodecyl sulfate (SDS) and their mixture) were added into the stock solution system. The solution systems with emulsifiers were observed under optical microscope and evaluated by using a differential scanning calorimeter (DSC); the results showed that only the solution system with the mixture of OP-10 and SDS transformed into PCM microemulsion, corresponding to the success of fiber formation by wet spinning. In addition, the microemulsion had a stable thermal property based on the DSC result, in which the latent heat capacity remained at 97.3% after 100 cycles of heating and cooling. The thermo-regulating alginate fiber was evaluated in terms of morphology, thermogravimetric (TG) analysis and differential scanning calorimetry. The results showed that the fiber had a smooth surface and porous structure in the cross-section, the bimodal TG curve of alginate fiber indicated that the PCM was successfully embedded into fiber and the DSC results demonstrated that the thermo-regulating alginate fiber had a comfortable phase change temperature of 25-35celcius, and an acceptable phase change enthalpy of about 20 J/g.
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    An analysis of effective thermal conductivity of heterogeneous materials
    (Technical University of Lodz, 2014-01-01) Zhu, Guocheng; Křemenáková, Dana; Wang, Yan; Militký, Jiří; Mazari, Funda Buyuk
    Effective thermal conductivity (ETC) is a very important index for evaluating the thermal property of heterogeneous materials, which include more than two different kinds of materials. Several analytical models were proposed for predicting the ETC of heterogeneous materials, but in some cases, these models cannot provide very accurate predictions. In this work, several analytical models and numerical simulations were studied in order to investigate the differences among them. In addition, some factors which would influence the ETC of heterogeneous materials were investigated by numerical simulation. The results demonstrated that the numerical simulation can provide very accurate prediction, indicated that different analytical models should be selected to predict specific problems based on their assumptions, and suggested that more variables need to be considered in order to improve these analytical models, such as inclusion shape, inclusion size, distribution of inclusions and contact area. Besides, numerical method could be an effective and reliable way to obtain the ETC of heterogeneous materials with any kind of complicated structures. © AUTEX.
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    Badanie właściwości zasysania wody (efekt knota) tkanin bawełnianych
    (Institute of Biopolymers and Chemical Fibres, 2015-01-01) Zhu, Guocheng; Militký, Jiří; Wang, Yan; Sundarlal, Bele Vijay; Křemenáková, Dana
    In order to study the heat and moisture comfort, the wicking property of textiles has been used as an important and effective index. In this paper, the wicking behaviour of cotton fabric in the warp and weft directions was investigated in terms of the wicking height, rate of wicking, mass increment distribution per centimetre of the wicking height, and the durative wicking height after removal of the wicking liquid reservoir. The results showed that the wicking height square had a good correlation with the time in both the warp and weft directions. The wicking rate was higher in the weft direction than that in the warp, especially at the beginning of the wicking process. The mass increment of fabric per centimetre of the wicking height was inversely proportional to the wicking height; the mass of water absorbed in the fabric did not have a significant difference in the weft and warp directions. © 2015, Institute of Biopolymers and Chemical Fibres. All rights reserved.
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    Co-solvent free interfacial polycondensation and properties of polyurea PCM microcapsules with dodecanol dodecanoate as core
    (Elsevier Ltd, 2020-03-01) Cai, Changwei; Ouyang, Xu; Zhou, Lan; Liu, Guojin; Wang, Yan; Zhu, Guocheng; Yao, Juming; Militký, Jiří; Venkataraman, Mohanapriya; Zhang, Guoqing
    A kind of eco-friendly micro-encapsulated phase change materials (MEPCM) with dodecanol dodecanoate as core material were synthesized via the interfacial polymerization of toluene-2, 4-diisocyanate (TDI) and diethylenetriamine (DETA). During the preparation, a facile solvent free synthesis route was developed owing to the good compatibility of TDI and dodecanol dodecanoate. The synthesized MEPCM were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Particle Size Distribution (PSD) analyzer, Differential Scanning Calorimetry (DSC), Thermogravimetric/Infrared spectrometry (TG-IR) and thermal constants analyzer. It is found that the resultant MEPCM in nearly spherical shape are in the size scope from 10.0 to 40.0 μm, have the average latent heat in the range of 103.4–140.3 J/g, and exhibit high temperature resistance with an onset evaporation temperature at 234.0 °C. Moreover, the MEPCM possess good thermal conductivity from 0.17 W/m K to 0.21 W/m K. Therefore, it is confirmed that the prepared MEPCM can be regarded as a promising thermal energy storage material appropriate to the thermo-regulating fields such as renewable solar heating system.
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    Comparison of effective thermal conductivity of hollow fibers by prediction models and FE method
    (Trans Tech Publications Ltd, 2013-01-01) Zhu, Guocheng; Militký, Jiří; Wang, Yan; Huang, Juan; Křemenáková, Dana
    In order to evaluate the effective thermal conductivity (ETC) of hollow fibers, three theoretical models (the parallel/series model, quadrate model and cylindrical model) and finite element method carried out by ANSYS simulation were studied. The results showed that different theoretical models gave quite different effective thermal conductivities. The results from theoretical models and simulations were completely identical in the case when models had regular structures and the heating surface was the same kind of material. The ETC of hollow fibers from all of theoretical models and simulations decreased exponentially with the increase of air volume content. In addition, the ETC of hollow fibers from the first theoretical model were a bit higher than the results from simulation, whereas those from the second theoretical model were smaller than the results from simulation, and those from the third theoretical model were identical to the results from simulation. © (2014) Trans Tech Publications, Switzerland.
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    Performance of Electrospun Polyvinylidene Fluoride Nanofibrous Membrane in Air Filtration
    (2019-01-01) Xiao, Yuanxiang; Wen, Enlong; Sakib, Nazmus; Yue, Zhonghua; Wang, Yan; Cheng, Si; Militký, Jiří; Venkataraman, Mohanapriya; Zhu, Guocheng
    Polyvinylidene fluoride (PVDF) fibrous membranes with fiber diameter from nanoscale to microscale were prepared by electrospinning. The structural parameters of PVDF fibrous membrane in terms of fiber diameter, pore size and its distribution, porosity or packing density, thickness, and areal weight were tested. The relationship between solution concentration and structural parameters of fibrous membrane was analyzed. The filtration performance of PVDF fibrous membrane in terms of air permeability and filtration efficiency was evaluated. The results demonstrated that the higher solution concentration led to a larger fiber diameter and higher areal weight of fibrous membrane. However, no regular change was found in thickness, porosity, or pore size of fibrous membrane under different solution concentrations. The air permeability and filtration efficiency of fibrous membrane had positive correlations with pore size. The experimental results of filtration efficiency were compared with the predicted values from current theoretical models based on single fiber filtration efficiency. However, the predicted values did not have a good agreement with experimental results since the fiber diameter was in nanoscale and the ratio of particle size to fiber diameter was much larger than the value that the theoretical model requires.
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    Preparation of Electrosprayed, Microporous Particle Filled Layers
    (MDPI, 2020-06-15) Venkataraman, Mohanapriya; Yang, Kai; Xiong, Xiaoman; Militký, Jiří; Křemenáková, Dana; Zhu, Guocheng; Yao, Juming; Wang, Yan; Zhang, Guoqing
    Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer known for its excellent hydrophobic properties. In this work, samples from PTFE dispersions with different combinations of water and carbon microparticles were prepared using an electrospraying method. The morphologies and sizes of carbon particles were investigated and the properties of layers including roughness, hydrophobicity and electrical resistivity were investigated. The non-conductive carbon microparticles were selected as a model particle to check the compatibility and electrospraying ability, and it had no effect on the hydrophobic and electrical properties. Carbon microparticles in polymer solution increased the degree of ionization and was found to be beneficial for the shape control of materials. The results showed that PTFE dispersion with the composition of water and carbon microparticles produced fine sphere particles and the layer fabricated with increased roughness. It was also found that the electrical resistivity and hydrophobicity of all the layers comparatively increased. The fabricated microporous layers can be used in various applications like interlining layer in multilayer textile sandwiches.
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    Selected Sorption Properties of Nanofibers Assembly
    (Technická Univerzita v Liberci, 2016-01-01) Wang, Yan
    Polyamidy byly syntetizovány poprvé v roce 1935 a od té doby jejich počet i výroba prudce roste. Vlákna z polyamidu 6 jsou v důsledku svých vynikajících vlastností jedním z široce používaných syntetických vláken v textilní oblasti. Vlákna z polyamidu 6 jsou studována jako sorbenty barviv, iontů těžkých kovů, pesticidů atd. Nicméně s růstem rychlosti rozvoje nanotechnologií, včetně elektrického zvlákňování a dalších technologií přípravy nanočástic, se mění život lidí ve všech oblastech a chování nanovlákenných soustav se stává důležitou otázkou. Systematický výzkum sorpční vlastnosti systémů polyamidových nanovláken je podstatou této práce. Před začátkem výzkumu byl proveden podrobný přehled literatury, pro identifikaci mezer v současných znalostech této problematiky, které budou doplněny v této práci. Byly studovány zejména teorie sorpce v systémech tuhá látka-kapalina, termodynamika sorpce, fotokatalýza, použití polyamidových nanovláken a nanočástic oxidu titaničitého. Zejména při využití sorpce a fotokatalýzy se očekává, že umožní optimální odstranění organických látek z vodných systémů. V této práci byly nanotechnologie implementovány do reálné studie adsorpčních vlastností soustav nanovláken na bázi polyamidu 6. Jako modelový sorbent pro sledování adsorpčních vlastností bylo vybráno organické barvivo. Byly stanoveny statické a dynamické sorpční vlastnosti soustavy nanovláken z polyamidu 6, byly využity kinetické a termodynamické modely, depozice nanočástic oxidu titaničitého a parní aktivace polyamidových nanovláken. Statická sorpční a studie odhalila, že termodynamická Langmuirova izoterma a kinetická rovnice pseudodruhého řádu dobře vyhovuje při popisu sorpce pro experimentální data ze spontánní sorpčního procesu kyselého barviva do struktury nanovláken z polyamidu 6. Parní aktivace polyamidu při teplotě nad 120 ° C vedla ke zvýšení statické sorpce kyselého barviva do soustavy nanovláken z polyamidu 6. Studie dynamické sorpce ukázala, že nanovlákna mají lepší sorpční vlastnosti vůči barvivům barviva než konvenční vlákna. Sorpční kapacita nanovláken z polyamidu 6 vůči hormonům i barvivům vykazovaly přímou úměru ke specifickému povrchu vláken. Fotokatalytické nanočástice TiO2 vykazovaly samočisticí schopnosti při koncentraci nad 18 mg/m2 a době ozařování UV světlem vyšší než 90 minut. Sorpce barviva do nanovlákenného sorbentu ovlivnila samočisticí efekt a fotokatalytické TiO2 nanočástice se ukázaly být jednou z metod pro zlepšení snížení koncentrace barviva Acid Orange 7 v roztoku. Odbarvování odpadní vody s obsahem rozpustných barviv by být jedním z možných aplikací této metody.
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    Simulation of airflow motion in jet nozzle with different geometric parameters
    (Trans Tech Publications Ltd, 2013-01-01) Zhu, Guocheng; Ibrahim, Sayed M.; Militký, Jiří; Wang, Yan; Křemenáková, Dan
    Jet nozzle with tangentially injected airflow has been applying into spinning technology due to the tangential force produced by swirling airflow. In order to understand the airflow motion trajectory in jet nozzle, modify the nozzle structure and dimension, FLUENT software program is used. Some parameters which are closely related the airflow motion profiles are studied, such as the diameter of nozzle chamber, the diameter and angle of the orifice. The results showed that the intensity of air swirling is more strong in a smaller nozzle chamber; a larger orifice diameter is helpful for producing strong yarn and improving production efficiency, but it requires a larger nozzle chamber, therefore, a reasonable rate of orifice and nozzle chamber diameter is important; as the orifice angle increases, the tangential velocity decreases, which decreases the intensity of airflow swirling, and a small orifice angle will cause a larger reverse jet, which is bad to draw the fibers into the nozzle. © (2013) Trans Tech Publications, Switzerland.
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    Study on the Relationship between Structure Parameters and Filtration Performance of Polypropylene Meltblown Nonwovens
    (Sciendo, 2019-01-01) Xiao, Yuanxiang; Sakib, Nazmus; Yue, Zhonghua; Wang, Yan; Cheng, Si; You, Jianmin; Militký, Jiří; Venkataraman, Mohanapriya; Zhu, Guocheng
    In this study, polypropylene meltblown nonwoven fabrics with different structure parameters such as fiber diameter, pore size, and areal density were prepared by the industrial production line. The morphology of meltblown nonwoven fibers was evaluated by using scanning electron microscope, and the diameter of fibers was analyzed by using image-pro plus software from at least 200 measurements. The pore size of nonwoven fabric was characterized by a CFP-1500AE type pore size analyzer. The filtration efficiency and pressure drop were evaluated by TSI8130 automatic filter. The results showed that the pressure drop of nonwoven fabrics decreased with the increase in pore size; the filtration efficiency and the pressure drop had a positive correlation with the areal density. However, when the areal density is in the range of 27-29 g/m2, both filtration efficiency and pressure drop decreased with the increase of areal density; when the areal density was kept constant, the filtration efficiency decreased as the pore size decreased; when the pore size of the meltblown nonwoven fabric is less than 17 μm, the filtration efficiency increased as the pore diameter decreased; when the pore diameter of the nonwoven fabric is larger than 17 μm. In a wide range, the pressure drop decreased as the fiber diameter decreased.
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    Study on the Wicking Property of Cotton Fabric
    (Inst Chemical Fibres, 2015-01-01) Zhu, Guocheng; Militký, Jiří; Wang, Yan; Sundarlal, Bele Vijay; Křemenáková, Dana
    In order to study the heat and moisture comfort, the wicking property of textiles has been used as an important and effective index. In this paper, the wicking behaviour of cotton fabric in the warp and weft directions was investigated in terms of the wicking height, rate of wicking, mass increment distribution per centimetre of the wicking height, and the durative wicking height after removal of the wicking liquid reservoir The results showed that the wicking height square had a good correlation with the time in both the warp and weft directions. The wicking rate was higher in the weft direction than that in the warp, especially at the beginning of the wicking process. The mass increment of fabric per centimetre of the wicking height was inversely proportional to the wicking height; the mass of water absorbed in the fabric did not have a significant difference in the weft and warp directions.
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    Wicking property of cotton fabric in different directions
    (Fiber Society, 2014-01-01) Zhu, Guocheng; Militký, Jiří; Wang, Yan; Křemenáková, Dana
    The wicking behavior has been used as an important and effective index for investigating the heat and moisture comfort, therefore, the wicking behavior of cotton fabric in warp and weft direction was studied.