Thermal conductivity of wool/pet weaves

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.It is well known that thermal conductivity of fabric is mainly influenced by their porosity. The fabric porosity is a function of construction parameters such as yarn fineness and set of weft and warp. The ideal volume porosity can be computed from basic fabric parameters and the structure of elementary cell. The main aim of this work is the creation of simple mechanistic model for the prediction of fabric thermal conductivity from basic fabric properties such as yarn diameters, weft and warp sett, planar weight and thickness of fabric. This model is in fact the combination of air conductivity and conductivity of fibrous phase in hierarchy fibers, yarn and fabric. The experimentally obtained thermal conductivities of 27 wool/PET plain weaves with constant sett of warp and varying sett of weft and varying yarn fineness are used for checking of the predictive ability of this model.vk201

Complex characterization of cotton fabric thermo physiological comfort

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.The main aim of this paper is evaluation of physiological Index of Comfort IC as a complex combination of individual fabrics properties connected with physiological comfort. The influence of the cotton fabrics structure on the selected parameters characterizing the physiological comfort of fabrics is investigated as well. The structural parameters of woven fabrics are collected into total volume porosity. Measurements of the thermal insulation parameters are performed by the sweating guarded hotplate test. Assessment of the air permeability is performed according to the procedure described in standard. The correlations between total volume porosity and above mentioned properties influencing the physiological comfort are investigated.pm201

A simple methods for prediction of textile fabrics thermal conductivity

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The prediction of the thermal conductivity of fibrous structures is important for design purposes of new fabrics and prediction of their thermal comfort. It is well known that physiological comfort is strongly connected with the thermal comfort. There is a lot of fabrics’ properties which influence the thermal comfort. Thermal insulation properties characterized by thermal resistance or thermal conductivity belong to the most important ones. There exists a plenty of various models for prediction of thermal conductivity of multiphase materials which can be used for prediction of textile fabrics thermal conductivity. Tai deduced mathematical expressions for the equivalent thermal conductivity of two and three-dimensional orthogonally fibre-reinforced composites in a one-dimensional heat flow model. Tai showed that whether a square slab model or a cylindrical fibre model is used makes little difference to the heat flux; while the fibre volume fraction matters. Transversal heat conductivity of fibrous composites is dependent on the yarn shape and fabric macroscopic porosity. Krach and Advani investigated the effect of void volume and shape on the effective conductivity of a unidirectional sample of a 3-phase composite using a numerical approach consisting of a unit cell. Their findings clearly showed that the influence of porosity on thermal conductivity could not be described solely by the void volume. Militky used the plain weave cell model for prediction of cotton type fabrics thermal conductivity. Application of these models for systems in which in matrix phase replaced by air phase is complicated by fact that during measurement of thermal conductivity is fabric deformed, shape of yarns is not circular and therefore unit cell is then not precisely known. The simpler approach is to use estimated porosity and packing density as characteristics of fabrics porous structure. The main aim of this paper is prediction of textile fabrics thermal conductivity as function of material (fibre type) and construction parameters (porosity or packing density). The relations between thermal conductivity and sound velocity or electrical conductivity are mentioned. Some approaches to predict thermal conductivity of multiphase systems with specific geometrical arrangements are shown. A measurement of the thermal conductivity is performed by the Alambeta apparatus. The set of cotton fabrics with plain weave and varying fineness of weft yarns is used as experimental material. The relations between total volume porosity and thermal conductivity of cotton weaves are predicted.cs201

On the eliminating attempts toward Šesták–Berggren equation

Některé nedávné komentáře pochybují o originalitě Šestáka-Berggrenovy rovnice, přestože dosud téměř dosáhla Osm set citačních odpovědí. Hodnota rovnice SB je zkoumána z hlediska obecné logistické rovnice ukazující její Odlišná filozofická strategie od odlišného ortodoxního geometrického modelování v kinetice. Použití připojených výrazů "Zkrácený" a "rozšířený" je zpochybněn.Some recent commentaries doubt the originality of Šesták–Berggren equation even though it received until today almost eight hundred citation responses. The worth of SB equation is examined in terms of general logistic equation showing its divergent philosophical strategy from dissimilar orthodox geometrical modeling in kinetics. The use of appended terms ‘truncated’ and ‘extended’ is questioned