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3D Numerical Simulation of Laminar Flow and Conjugate Heat Transfer through Fabric

Zhu G., Kremenakova D., Wang Y., Militky J., Mishra R., Wiener J.

Autex Research Journal

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2017

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Vol. 17, no. 1

53--60

EN

The air flow and conjugate heat transfer through the fabric was investigated numerically. The objective of this paper is to study the thermal insulation of fabrics under heat convection or the heat loss of human body under different conditions (fabric structure and contact conditions between the human skin and the fabric). The numerical simulations were performed in laminar flow regime at constant skin temperature (310 K) and constant air flow temperature (273 K) at a speed of 5 m/s. Some important parameters such as heat flux through the fabrics, heat transfer coefficient, and Nusselt number were evaluated. The results showed that the heat loss from human body (the heat transfer coefficient) was smallest or the thermal insulation of fabric was highest when the fabric had no pores and no contact with the human skin, the heat loss from human body (the heat transfer coefficient) was highest when the fabric had pores and the air flow penetrated through the fabric.

2

Air Permeability of Polyester Nonwoven Fabrics

Zhu G., Kremenakova D., Wang Y., Militky J.

Autex Research Journal

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2015

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Vol. 15, no. 1

8--12

EN

Air permeability is one of the most important properties of non-woven fabrics in many applications. This paper aims to investigate the effects of thickness, porosity and density on the air permeability of needle-punched non-woven fabrics and compare the experimental values with two models which are based on hydraulic radius theory and drag theory, respectively. The air permeability of the samples was measured by an air permeability tester FX3300. The results showed that the air permeability of non-woven fabrics decreased with the increase in thickness and density of samples, increased with the increase of porosity, and the air permeability was not directly proportional to the pressure gradient. Meanwhile, the prediction model based on hydraulic radius theory had a better agreement with experimental values than the model based on drag theory, but the values were much higher than the experimental results, especially for higher porosity and higher pressure gradient.

3

An analysis of effective thermal conductivity of heterogeneous materials

Zhu G., Kremenakova D., Wang Y., Militky J., Mazari F. B.

Autex Research Journal

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2014

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Vol. 14, no. 1

14--21

EN

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.

4

Structural design engineering of woven fabric by soft computing: part II - non-plain weave

Mishra R., Kremenakova D., Behera B K, Militky J.

Autex Research Journal

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2011

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Vol. 11, no. 2

42--46

EN

The maximum weavability limit is predicted by extending Peirce's geometrical model for non-plain weaves for circular and racetrack cross-sections by soft computing. This information is helpful to weavers in that attempts to weave impossible constructions can be avoided, thus saving time and money. It also helps in anticipating difficulties in weaving and in taking the necessary steps in warp preparation. The relationship between the cover factors in the warp and weft directions is demonstrated for circular and racetrack cross-sections for plain, twill, basket and satin weave. Non-plain weave fabric affords further flexibility for increasing fabric mass and fabric cover. As such, they enlarge the scope of the fabric designer.

5

Structural design engineering of woven fabric by soft computing: part I - plain weave

Mishra R., Kremenakova D., Behera B K, Militky J.

Autex Research Journal

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2011

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Vol. 11, no. 2

37--41

EN

An attempt has been made to optimise the engineering attributes of a plain weave fabric according to certain requirements. A simplified algorithm was used to solve fabric geometrical model equations, and relationships were obtained between useful fabric parameters such as thread spacing and crimp, fabric cover and crimp, warp and weft cover. Such relationships help in guiding the direction for moderating fabric parameters. The full potential of the Peirce fabric geometrical model for plain weave has been exploited by soft computing. The interrelationships between different fabric parameters for jammed structures, non-jammed structures and special cases in which the cross-threads are straight were obtained using a suitable algorithm. It is hoped that the fabric designer will benefit from the flexibility in choosing fabric parameters for achieving any end use with the desired fabric properties.