Numerical modelling and experimental study of heat and moisture properties of a wall based on date palm fibers concrete

In the present paper, we study with both experimental and numerical aspect the heat and moisture transfer properties of a wall based on concrete filled with the natural fibers. The wall was placed in climatic chamber and temperature and relative humidity were monitored at different depths. A developed model describing heat and moisture transfers in porous building materials was implemented in COMSOL Multiphysics and solved with the finite element method. The obtained results are compared with experimental data. A relatively good agreement was obtained for both temperature and relative humidity variation at different depths. Finally, the developed model gives almost a good prediction despite the classical difficulties encountered at the experiment, which is very promising for the prediction of the hygrothermal behavior of bio-based building materials at different conditions

Étude des propriétés thermophysiques et électriques de matériaux hétérogènes

Ce travail présente une étude comparative des propriétés thermiques, électriques rhéologiques et diélectriques de trois systèmes composites : EVA chargé de billes de verre argentées et non argentées, EVA chargé de poudres de BaTiO3, et PVC chargé de nanotubes de carbone. Cette étude est consacrée dans un premier temps à l élaboration des échantillons et à la détermination de la conductivité électrique ( ), de la conductivité thermique (k), de la viscosité dynamique ( ) et de la permittivité diélectrique relative ( r) (pour certains composites). Il a été démontré dans ce travail que l effet de la taille des charges est significatif sur les propriétés électriques et diélectriques (diminution du seuil de percolation et de r) et négligeable sur les propriétés thermiques et rhéologiques. En outre, l effet de la surface externe des charges est très important sur k et s il existe des contacts entre les charges au sein de la matrice. Par ailleurs, des corrélations ont été constatées entre k et les autres propriétés de transport ( , et r). Parallèlement à ce travail, une amélioration d une méthode radiométrique périodique utilisant la thermographie infrarouge et permettant la mesure simultanée de l'émissivité, de la conductivité et de la diffusivité thermique de matériaux opaques a été mise en place. La méthode et le dispositif de mesure ont été validés en étudiant un matériau de propriétés connues (PVC) à température ambiante. Cette validation comprend une étude de la reproductibilité de la méthode, une comparaison aux résultats de la littérature, une analyse des sources d'incertitudes ainsi qu'une analyse de sensibilité pour l échantillon de PVC.This work presents a comparative study of thermophysical, electrical, dielectric and rheologic properties of three composites: glass and silver coated glass spheres dispersed in EVA matrix, powders of BaTiO3 dispersed in EVA matrix and PVC matrix filled with Carbon NanoTubes. This study is devoted in the first time to the composites preparation and to the measurements of the electrical conductivity ( ), thermal conductivity (k), dynamic viscosity ( ) and the relative permittivity ( r) (for some composites). It was shown that both relative permittivity r and electrical conductivity depend on the fillers size. However, the effect of the particles size on the thermal and the rheologic properties can be neglected. Besides, the fillers surface is an important factor controlling the thermal and the electrical conductivities. It also follows from this study the existence of a correlation between the thermal conductivity and others properties ( , and r). The second objective of this study was the improvement of a measurement method of emissivity, thermal conductivity and diffusivity. The characterisation of a reference sample (PVC) allowed the validation of the measurement protocol. This includes the reproducibility study of the method, the comparison of the results to the literature data, the analysis of the limitations of the measurement protocol and a sensitivity analysis.PARIS12-CRETEIL BU Multidisc. (940282102) / SudocSudocFranceF

Analytical and Numerical Investigation on Effective Thermal Conductivity of Polymer Composites Filled with Conductive Hollow Particles

International audienc

Experimental investigation of new biocomposite with low cost for thermal insulation

International audienc

Hygric properties and thermal conductivity of a new insulation material for building based on date palm concrete

International audienceExperimental investigations of hygric and thermal conductivity properties of a new biocomposite material dedicated for construction which contains cement, sand and water and reinforced with 15 wt% of date palm fibers were carried out. The investigations were based on the measurement of water vapor permeability, of sorption isotherm, of moisture diffusivity and thermal conductivity. The results reveal that the presence of date palm fibers improves the performance and the efficiency of the composite material: lowering of water vapor diffusion resistance, enhancement of moisture transfer. The results were compared to other kind of biocomposite materials used for construction. Finally, we have shown the effect of temperature on thermal conductivity for both moist and dry states

Numerical Investigation of Heat Transfer of Silver-Coated Glass Particles Dispersed in Ethylene Vinyl Acetate Matrix

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Investigation on heat and moisture transfer in bio-based building wall with consideration of the hysteresis effect

International audienceTwo mathematical models describing heat and moisture transfer in porous media were used to predict the hygrothermal behavior of a new type of bio-based materials made of date palm concrete (DPC). The finite element method was used for the resolution of partial differential equations and numerical results were compared to experimental data considering similar conditions of temperature and relative humidity through the DPC wall. At first, a mesh sensitivity analysis was carried out and the optimum mesh configuration was determined. Afterwards, the hysteresis effect was implemented in the models and its influence on the variation of the relative humidity through the wall was discussed. The results revealed that the proposed models globally provided satisfactory results for the DPC wall, with an improved accuracy when considering the hysteresis effect. Finally, a comparison in terms of thermal insulation and moisture buffering capacity between DPC and a classical building material was performed numerically. Results showed that the new bio-based wall is very promising and can contribute to mitigate temperature variation and ensure hydrothermal comfort in buildings

A comparative analysis of dielectric, rheological and thermophysical behaviour of ethylene vinyl acetate/BaTiO3 composites

International audienceDielectric, rheological and thermal behaviours of ethylene vinyl acetate/barium titanate sphere (EVA/BaTiO3) composite materials were investigated in this work. Several composites were prepared for different volume concentrations (from 5% to 49%) and for two types of spheres sizes d: d = 9 µm and d = 105 µm. We show that the use of larger particles allows an increase of dielectric permittivity and thermal conductivity, particularly at high filler concentrations. A comparison between the thermal, dielectric and rheological behaviours of the composites is also reported in this paper. A linear dependence of the relative variation of thermal conductivity and dielectric permittivity, on the one hand, and thermal conductivity and Newtonian viscosity, on the other, was shown

Experimental and modeling study of effective thermal conductivity of polymer filled with date palm fibers

International audienc

A comparative analysis of dielectric, rheological and thermophysical behaviour of ethylene vinyl acetate/BaTiO3 composites

International audienceDielectric, rheological and thermal behaviours of ethylene vinyl acetate/barium titanate sphere (EVA/BaTiO3) composite materials were investigated in this work. Several composites were prepared for different volume concentrations (from 5% to 49%) and for two types of spheres sizes d: d = 9 µm and d = 105 µm. We show that the use of larger particles allows an increase of dielectric permittivity and thermal conductivity, particularly at high filler concentrations. A comparison between the thermal, dielectric and rheological behaviours of the composites is also reported in this paper. A linear dependence of the relative variation of thermal conductivity and dielectric permittivity, on the one hand, and thermal conductivity and Newtonian viscosity, on the other, was shown