22 research outputs found
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