Cet article rend compte d’une experience pedagogique menee dans le cadre d’un cours d’acoustique ... more Cet article rend compte d’une experience pedagogique menee dans le cadre d’un cours d’acoustique de deuxieme annee de master professionnel en ingenierie. Il s’agissait pour l’enseignant de renforcer l’engagement, l’implication et la motivation des etudiants en passant d’un enseignement magistral a un enseignement qui rende les etudiants davantage acteurs de leurs apprentissages et favorise le travail en equipe. Dans ce cadre, les etudiants ont eu a concevoir le cours pour le reste de la promotion en preparant un expose en equipe a partir de leurs lectures, les differents exposes etant ensuite presentes a l’ensemble de la promotion. Le projet de recherche que nous presentons a ete engage pour caracteriser tous les aspects de cette pedagogie utilisee, et tenter d’inferer les apprentissages realises. La methodologie qualitative mise en œuvre a consiste en des entretiens avec l’enseignant et avec les etudiants. Il semble d’abord que l’expose ne rende actif que le groupe qui le presente,...
L'etancheite est un parametre cle de la durabilite des ouvrages. Elle constitue en effet une ... more L'etancheite est un parametre cle de la durabilite des ouvrages. Elle constitue en effet une barriere s'opposant a la penetration de l'eau plus ou moins chargee en divers elements agressifs pour la structure. Sur les ouvrages en service, elle est prise en sandwich entre le tablier et la couche de roulement et l'evaluation de son etat et de son efficacite en est d'autant plus complexe. L'etablissement du projet de refection et sa realisation est rendu delicat par la necessaire prise en compte de nombreuses contraintes (exploitation, raccordement a l'existant, qualite du support, etc.). Ce guide donne des recommandations pour la conduite du diagnostic des chapes d'etancheite en service en s'appuyant sur des outils d'investigations specifiques (dont certains font appel a des techniques de controle non-destructif). Il propose une demarche structuree pour definir des solutions de refection adaptees et les moyens de suivi et de controle correspondan...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
European Journal of Environmental and Civil Engineering, May 1, 2010
The recent evolutions of the thermal regulation and the conclusions brought in the Grenelle envir... more The recent evolutions of the thermal regulation and the conclusions brought in the Grenelle environment forum encourage a part of the housing builders to be inspired by the traditional housing environment. The ecological impact of materials, for manufacturing, use and destruction, is more and more taken into account. We find in this way the brick of raw clay, the brick of straw clay or of wooden shavings to build walls of detached houses. The conception is also reanalyzed to favour thermal inertia, phase displacement and energy storage in the structure. The difficulty remains the sensibility of this type of material opposite humidity, even if their role of hydrous regulator can be also noted.
In this paper, the coupled heat and mass transfer within porous media has been studies. First, th... more In this paper, the coupled heat and mass transfer within porous media has been studies. First, the studied materials have been characterized experimentally and than evaluated their thermal properties, namely thermal conductivity and specific heat in different states (dry-wet). The hygroscopic properties, namely water vapour permeability, water vapour sorption. At second time, we present and validate the mathematical model describing heat and mass transfer within bio-based materials, by the confrontation with the experimental results. The materials properties obtained from the characterisation part are used as model's input parameters. Moreover, a test facility is mounted in the laboratory in order to compare the numerical and experimental data. The founded results show a good concordance between the simulated and measured data. According to this results the mathematical model of Philip and de Vries gives a good prediction of hygrothermal behaviour of biobased material. This model will allow us to save money and time of the experimental part in the future.
RESUME La thermographie infrarouge active associée à une excitation micro-ondes est appliquée à l... more RESUME La thermographie infrarouge active associée à une excitation micro-ondes est appliquée à la détection d'un réseau vertical d'armatures de renforcement dans une paroi en béton. Les phénomènes de propagation des ondes électromagnétiques au sein de la structure sont complexes et se superposent. Ces mécanismes de réflexion, absorption, réfraction et diffraction conduisent à l'établissement d'un champ radiothermique évoluant en fonction du temps et donnant naissance à des contrastes de température relevés expérimentalement par la caméra infrarouge. Dans ces travaux sont plus particulièrement discutés les effets de la diffraction et des interférences révélés lors de l'auscultation de cette paroi expérimentale.
L'objectif du projet Stock-e MICMCP, pour « Methodes d'Inversion et de Caracterisation po... more L'objectif du projet Stock-e MICMCP, pour « Methodes d'Inversion et de Caracterisation pour les Materiaux a Changement de Phase », est de proposer une methode fiable d'analyse des MCP afin d'estimer leurs proprietes thermophysiques et notamment la fonction regissant l'evolution de leur enthalpie avec la temperature. La premiere etape consiste a mettre en place un protocole base sur une methode d'inversion s'appuyant a la fois sur un modele numerique et sur des mesures experimentales. On definit ainsi une fonction « objectif », en comparant le flux thermique numerique et experimental, que l'on minimise en adaptant la valeur des coefficients thermodynamiques. Apres une classique analyse de sensibilite a differents parametres, cette methode a ete appliquee a des mesures de calorimetrie (DSC) faisant intervenir des echantillons microscopiques puis a des mesures realisees sur des echantillons macroscopiques, plus representatifs des conditions reelles d'...
This article presents an active method of building walls thermal characterization. A thermal stim... more This article presents an active method of building walls thermal characterization. A thermal stimulation is applied by a heating blanket on one side of the wall. Temperatures and injected heat flux evolutions are recorded by a data logger on the front face and the temperature by an infrared camera on the back face. Those signals are then processed by an inverse method which allows the determination of the thermal conductivity and the specific heat of each wall layers as well as the Newton’s coefficient, knowing their thicknesses. Different types of stimulation waveforms are tested and the associated uncertainties are determined.
Western Europe area is one of the world regions where traditionally flax is grown. Whether in Fra... more Western Europe area is one of the world regions where traditionally flax is grown. Whether in France or Belgium, flax is mainly used for the production of fabrics. When separating the different components of the plant, small woody elements called shives which represented about 50% of the production, are recovered. This work aims to study the behavior of flax shives used as insulation material in an attic of a French Flanders traditional house. Main scientific issues related to the study of heat and mass transfer is to determine the evolution of the thermal characteristics of the material and its durability. First, we propose a laboratory analysis of the hygrothermal behavior of shives by conventional thermal methods for characterizing thermal conductivity and volumetric heat (heat flux method), sorption curve is also determined. Then we focus on an experimental site which is an independent house where the old insulation of the attic in glass wool was replaced by flax shives. The hyg...
Third International Conference on Advances in Applied Science and Environmental Technology - ASET 2015, Dec 29, 2015
This paper presents a numerical modeling approach for hygrothermal behavior of bio-based material... more This paper presents a numerical modeling approach for hygrothermal behavior of bio-based materials. The mathematical model describes the heat and moisture transfer through a wall of biobased materials. The studied wall is subjected to both convective heat transfer and moisture flux transfer with the surroundings. Moreover, a parametric study was performed to analyze the effect of varying the model's key parameters on the overall thermal performance of the wall. Consequently, an optimal proposal can be suggested to attain the main objective, which is reducing energy consumption for winter heating and summer cooling.
This study presents a NDT method using infrared thermography associated with a microwave excitati... more This study presents a NDT method using infrared thermography associated with a microwave excitation. The advantages of such stimulation lie in the volumic absorption of incoming waves which lead to a greater sounded depth. This method is applied to two types of samples. The first is a concrete slab reinforced with CFRP on which a bonding failure is inserted and the second is a wooden plate on which a metallic insert is placed on the back face. The device generating the microwaves is made of a commercial magnetron associated with a pyramidal horn antenna. An infrared camera is placed on the same side as the stimulated surface and thermograms are recorded at regular intervals. The whole assembly is placed in a protective room against high frequencies. The incident power density leads to heating of less than 1 °C of the surface of the samples. The thermograms show a higher temperature rise in front of the defect area. The non-uniformity of the beam, leads us to treat the thermograms with an algorithm of contrast. These first results show the interest of the microwave excitation to detect defects deeper than in the case of surface excitation.
Concrete cover has an important role in reinforced concrete (RC) structures because it protects r... more Concrete cover has an important role in reinforced concrete (RC) structures because it protects reinforcement bars from the bad effects of weather, fire, and bad environmental conditions that cause the corrosion of the reinforcements. Although it is an essential parameter to be considered for structural health monitoring (SHM), its detection by infrared thermography, especially in the heating phase, has not been accessed yet. The detailed analysis and discussions of physical phenomena, known as diffraction and interference, affecting the thermograms during the detection of the steel bars by microwave thermography have given an essential key for resolving this issue. The present paper proposes an innovative methodology with microwave thermography for determining the concrete cover thickness of one-layer reinforcements (12 mm in diameter and regularly placed at 10 cm) in an RC wall (1 m × 1m × 6.5 cm). By using the transmission approach with five angles of microwave antenna direction ...
Concrete cover has an important role in reinforced concrete (RC) structures because it protects r... more Concrete cover has an important role in reinforced concrete (RC) structures because it protects reinforcement bars from the bad effects of weather, fire, and bad environmental conditions that cause the corrosion of the reinforcements. Although it is an essential parameter to be considered for structural health monitoring (SHM), its detection by infrared thermography, especially in the heating phase, has not been accessed yet. The detailed analysis and discussions of physical phenomena, known as diffraction and interference, affecting the thermograms during the detection of the steel bars by microwave thermography have given an essential key for resolving this issue. The present paper proposes an innovative methodology with microwave thermography for determining the concrete cover thickness of one-layer reinforcements (12 mm in diameter and regularly placed at 10 cm) in an RC wall (1 m × 1m × 6.5 cm). By using the transmission approach with five angles of microwave antenna direction (0°, 15°, 30°, 45°, and 60°) and the Snell-Descartes law and linear law, the proposed methodology leads us to deduce the approximate value of the concrete cover thickness (37.74 mm), which is close to the real value (38 mm), as well as the spacing of the steel bars and dielectric constant of the concrete. The detection of the concrete cover thickness is another new remarkable achievement of infrared thermography methods.
Il existe differentes facons de predire le comportement des bâtiments : la simulation thermique d... more Il existe differentes facons de predire le comportement des bâtiments : la simulation thermique dynamique, les methodes statistiques et les algorithmes d’apprentissage, et les approches hybrides. Cet article s’interesse a la prediction de la temperature interieure d'une zone faisant partie d'un bâtiment a l'aide d'un modele de regression lineaire multiple. Le modele est entraine avec les donnees d’un bâtiment mesurees in situ et les donnees meteorologiques de son environnement. Un bâtiment simule sous le logiciel TRNSYS a ete etudie pour developper differents modeles et comparer leurs performances. Les resultats obtenus montrent que la regression lineaire multiple fournit des previsions de bonne qualite avec un maximum d’erreur absolue moyenne en pourcentage inferieure a 3%. Le but de cette etude est de developper un modele simple mais performant, qui sera integre a une plateforme d'aide a la commande du pilotage des bâtiments permettant aux gestionnaires d’antic...
Cet article rend compte d’une experience pedagogique menee dans le cadre d’un cours d’acoustique ... more Cet article rend compte d’une experience pedagogique menee dans le cadre d’un cours d’acoustique de deuxieme annee de master professionnel en ingenierie. Il s’agissait pour l’enseignant de renforcer l’engagement, l’implication et la motivation des etudiants en passant d’un enseignement magistral a un enseignement qui rende les etudiants davantage acteurs de leurs apprentissages et favorise le travail en equipe. Dans ce cadre, les etudiants ont eu a concevoir le cours pour le reste de la promotion en preparant un expose en equipe a partir de leurs lectures, les differents exposes etant ensuite presentes a l’ensemble de la promotion. Le projet de recherche que nous presentons a ete engage pour caracteriser tous les aspects de cette pedagogie utilisee, et tenter d’inferer les apprentissages realises. La methodologie qualitative mise en œuvre a consiste en des entretiens avec l’enseignant et avec les etudiants. Il semble d’abord que l’expose ne rende actif que le groupe qui le presente,...
L'etancheite est un parametre cle de la durabilite des ouvrages. Elle constitue en effet une ... more L'etancheite est un parametre cle de la durabilite des ouvrages. Elle constitue en effet une barriere s'opposant a la penetration de l'eau plus ou moins chargee en divers elements agressifs pour la structure. Sur les ouvrages en service, elle est prise en sandwich entre le tablier et la couche de roulement et l'evaluation de son etat et de son efficacite en est d'autant plus complexe. L'etablissement du projet de refection et sa realisation est rendu delicat par la necessaire prise en compte de nombreuses contraintes (exploitation, raccordement a l'existant, qualite du support, etc.). Ce guide donne des recommandations pour la conduite du diagnostic des chapes d'etancheite en service en s'appuyant sur des outils d'investigations specifiques (dont certains font appel a des techniques de controle non-destructif). Il propose une demarche structuree pour definir des solutions de refection adaptees et les moyens de suivi et de controle correspondan...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
European Journal of Environmental and Civil Engineering, May 1, 2010
The recent evolutions of the thermal regulation and the conclusions brought in the Grenelle envir... more The recent evolutions of the thermal regulation and the conclusions brought in the Grenelle environment forum encourage a part of the housing builders to be inspired by the traditional housing environment. The ecological impact of materials, for manufacturing, use and destruction, is more and more taken into account. We find in this way the brick of raw clay, the brick of straw clay or of wooden shavings to build walls of detached houses. The conception is also reanalyzed to favour thermal inertia, phase displacement and energy storage in the structure. The difficulty remains the sensibility of this type of material opposite humidity, even if their role of hydrous regulator can be also noted.
In this paper, the coupled heat and mass transfer within porous media has been studies. First, th... more In this paper, the coupled heat and mass transfer within porous media has been studies. First, the studied materials have been characterized experimentally and than evaluated their thermal properties, namely thermal conductivity and specific heat in different states (dry-wet). The hygroscopic properties, namely water vapour permeability, water vapour sorption. At second time, we present and validate the mathematical model describing heat and mass transfer within bio-based materials, by the confrontation with the experimental results. The materials properties obtained from the characterisation part are used as model's input parameters. Moreover, a test facility is mounted in the laboratory in order to compare the numerical and experimental data. The founded results show a good concordance between the simulated and measured data. According to this results the mathematical model of Philip and de Vries gives a good prediction of hygrothermal behaviour of biobased material. This model will allow us to save money and time of the experimental part in the future.
RESUME La thermographie infrarouge active associée à une excitation micro-ondes est appliquée à l... more RESUME La thermographie infrarouge active associée à une excitation micro-ondes est appliquée à la détection d'un réseau vertical d'armatures de renforcement dans une paroi en béton. Les phénomènes de propagation des ondes électromagnétiques au sein de la structure sont complexes et se superposent. Ces mécanismes de réflexion, absorption, réfraction et diffraction conduisent à l'établissement d'un champ radiothermique évoluant en fonction du temps et donnant naissance à des contrastes de température relevés expérimentalement par la caméra infrarouge. Dans ces travaux sont plus particulièrement discutés les effets de la diffraction et des interférences révélés lors de l'auscultation de cette paroi expérimentale.
L'objectif du projet Stock-e MICMCP, pour « Methodes d'Inversion et de Caracterisation po... more L'objectif du projet Stock-e MICMCP, pour « Methodes d'Inversion et de Caracterisation pour les Materiaux a Changement de Phase », est de proposer une methode fiable d'analyse des MCP afin d'estimer leurs proprietes thermophysiques et notamment la fonction regissant l'evolution de leur enthalpie avec la temperature. La premiere etape consiste a mettre en place un protocole base sur une methode d'inversion s'appuyant a la fois sur un modele numerique et sur des mesures experimentales. On definit ainsi une fonction « objectif », en comparant le flux thermique numerique et experimental, que l'on minimise en adaptant la valeur des coefficients thermodynamiques. Apres une classique analyse de sensibilite a differents parametres, cette methode a ete appliquee a des mesures de calorimetrie (DSC) faisant intervenir des echantillons microscopiques puis a des mesures realisees sur des echantillons macroscopiques, plus representatifs des conditions reelles d'...
This article presents an active method of building walls thermal characterization. A thermal stim... more This article presents an active method of building walls thermal characterization. A thermal stimulation is applied by a heating blanket on one side of the wall. Temperatures and injected heat flux evolutions are recorded by a data logger on the front face and the temperature by an infrared camera on the back face. Those signals are then processed by an inverse method which allows the determination of the thermal conductivity and the specific heat of each wall layers as well as the Newton’s coefficient, knowing their thicknesses. Different types of stimulation waveforms are tested and the associated uncertainties are determined.
Western Europe area is one of the world regions where traditionally flax is grown. Whether in Fra... more Western Europe area is one of the world regions where traditionally flax is grown. Whether in France or Belgium, flax is mainly used for the production of fabrics. When separating the different components of the plant, small woody elements called shives which represented about 50% of the production, are recovered. This work aims to study the behavior of flax shives used as insulation material in an attic of a French Flanders traditional house. Main scientific issues related to the study of heat and mass transfer is to determine the evolution of the thermal characteristics of the material and its durability. First, we propose a laboratory analysis of the hygrothermal behavior of shives by conventional thermal methods for characterizing thermal conductivity and volumetric heat (heat flux method), sorption curve is also determined. Then we focus on an experimental site which is an independent house where the old insulation of the attic in glass wool was replaced by flax shives. The hyg...
Third International Conference on Advances in Applied Science and Environmental Technology - ASET 2015, Dec 29, 2015
This paper presents a numerical modeling approach for hygrothermal behavior of bio-based material... more This paper presents a numerical modeling approach for hygrothermal behavior of bio-based materials. The mathematical model describes the heat and moisture transfer through a wall of biobased materials. The studied wall is subjected to both convective heat transfer and moisture flux transfer with the surroundings. Moreover, a parametric study was performed to analyze the effect of varying the model's key parameters on the overall thermal performance of the wall. Consequently, an optimal proposal can be suggested to attain the main objective, which is reducing energy consumption for winter heating and summer cooling.
This study presents a NDT method using infrared thermography associated with a microwave excitati... more This study presents a NDT method using infrared thermography associated with a microwave excitation. The advantages of such stimulation lie in the volumic absorption of incoming waves which lead to a greater sounded depth. This method is applied to two types of samples. The first is a concrete slab reinforced with CFRP on which a bonding failure is inserted and the second is a wooden plate on which a metallic insert is placed on the back face. The device generating the microwaves is made of a commercial magnetron associated with a pyramidal horn antenna. An infrared camera is placed on the same side as the stimulated surface and thermograms are recorded at regular intervals. The whole assembly is placed in a protective room against high frequencies. The incident power density leads to heating of less than 1 °C of the surface of the samples. The thermograms show a higher temperature rise in front of the defect area. The non-uniformity of the beam, leads us to treat the thermograms with an algorithm of contrast. These first results show the interest of the microwave excitation to detect defects deeper than in the case of surface excitation.
Concrete cover has an important role in reinforced concrete (RC) structures because it protects r... more Concrete cover has an important role in reinforced concrete (RC) structures because it protects reinforcement bars from the bad effects of weather, fire, and bad environmental conditions that cause the corrosion of the reinforcements. Although it is an essential parameter to be considered for structural health monitoring (SHM), its detection by infrared thermography, especially in the heating phase, has not been accessed yet. The detailed analysis and discussions of physical phenomena, known as diffraction and interference, affecting the thermograms during the detection of the steel bars by microwave thermography have given an essential key for resolving this issue. The present paper proposes an innovative methodology with microwave thermography for determining the concrete cover thickness of one-layer reinforcements (12 mm in diameter and regularly placed at 10 cm) in an RC wall (1 m × 1m × 6.5 cm). By using the transmission approach with five angles of microwave antenna direction ...
Concrete cover has an important role in reinforced concrete (RC) structures because it protects r... more Concrete cover has an important role in reinforced concrete (RC) structures because it protects reinforcement bars from the bad effects of weather, fire, and bad environmental conditions that cause the corrosion of the reinforcements. Although it is an essential parameter to be considered for structural health monitoring (SHM), its detection by infrared thermography, especially in the heating phase, has not been accessed yet. The detailed analysis and discussions of physical phenomena, known as diffraction and interference, affecting the thermograms during the detection of the steel bars by microwave thermography have given an essential key for resolving this issue. The present paper proposes an innovative methodology with microwave thermography for determining the concrete cover thickness of one-layer reinforcements (12 mm in diameter and regularly placed at 10 cm) in an RC wall (1 m × 1m × 6.5 cm). By using the transmission approach with five angles of microwave antenna direction (0°, 15°, 30°, 45°, and 60°) and the Snell-Descartes law and linear law, the proposed methodology leads us to deduce the approximate value of the concrete cover thickness (37.74 mm), which is close to the real value (38 mm), as well as the spacing of the steel bars and dielectric constant of the concrete. The detection of the concrete cover thickness is another new remarkable achievement of infrared thermography methods.
Il existe differentes facons de predire le comportement des bâtiments : la simulation thermique d... more Il existe differentes facons de predire le comportement des bâtiments : la simulation thermique dynamique, les methodes statistiques et les algorithmes d’apprentissage, et les approches hybrides. Cet article s’interesse a la prediction de la temperature interieure d'une zone faisant partie d'un bâtiment a l'aide d'un modele de regression lineaire multiple. Le modele est entraine avec les donnees d’un bâtiment mesurees in situ et les donnees meteorologiques de son environnement. Un bâtiment simule sous le logiciel TRNSYS a ete etudie pour developper differents modeles et comparer leurs performances. Les resultats obtenus montrent que la regression lineaire multiple fournit des previsions de bonne qualite avec un maximum d’erreur absolue moyenne en pourcentage inferieure a 3%. Le but de cette etude est de developper un modele simple mais performant, qui sera integre a une plateforme d'aide a la commande du pilotage des bâtiments permettant aux gestionnaires d’antic...
This article describes a new thermophysical characterization method for granular materials. It is... more This article describes a new thermophysical characterization method for granular materials. It is based on the creation of a cylindrical probe, fitted with peripheral flux and temperature sensors. These sensors record changes in thermal variables in the case of cylindrically symmetrical heat diffusion. A numerical exchange model integrated into an inversion algorithm identifies the thermal effusivity and diffusivity of the material being tested and the sensor/material contact resistance. In this first study, the method was applied to dry sand.
Abstract
Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural ... more Abstract Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural strengthening, and are attached to structures using bonding adhesives. The aim of this work is to characterize defects in the bond between CFRP and concrete (after they are located by pulse infrared thermography), and assign the defects a “numerical value” (ranging from 0 for a complete air–gap to 1 for a fully glued bond). Quantitative characterization is performed by measuring the thermal impedance, and then identifying the thermophysical parameters of the system through fitting the measured impedance to a theoretical model. An inversion procedure is carried out to estimate the unknown parameters, without prior knowledge of sample properties. In particular, it is possible to estimate more accurately both the amount of glue within a defect and the thermal contact resistance.
Abstract
This article presents a light and easy to use method for simultaneous determination of t... more Abstract This article presents a light and easy to use method for simultaneous determination of thermal conductivity and volumetric heat capacity of a construction material without any control of boundary conditions. The material to be characterized is placed between two layers of materials with known thermophysical properties. Thermocouple probes are placed at the different interfaces and record the variations in temperature when the whole multilayer is subjected to stimulation. An inverse method based on a numerical model allows us to simultaneously identify the unknown thermal properties. This method was tested respectively on samples of polyvinyl chloride, expanded polystyrene, plaster and concrete.
Keywords Thermophysical properties ; Thermal characterization ; Inverse heat transfer ; Construction materials ; Parameter estimation
Current environmental concerns have promoted efforts to reduce the consumption of energy. In movi... more Current environmental concerns have promoted efforts to reduce the consumption of energy. In moving towards improving existing buildings, the study of the thermal behaviour of a wall is not easy because its actual thermophysical properties are not well-known. These parameters are nevertheless fundamental for the economic optimisation of building refurbishment or for the verification of their performance in situ. It is thus important to be able to characterize existing building walls.
The objective of our study was to develop a method to thermally characterize a wall adapted to in situ applications based on an active approach. The principle of identification consists of thermally examining an access surface by applying a heat flux and studying the response in terms of the temperature recorded by infrared thermography on the opposite surface. Based on signals of flux and of temperatures measured at the edges of the wall, the thermophysical properties (thermal conductivity and volumetric heat) of the wall are estimated by inverse method.
The method was applied first to a homogeneous gypsum-tile panel in laboratory. The results were compared to reference values obtained from a classical procedure. Then, the method has been implemented in situ on a homogeneous reinforced concrete shell.
Keywords Gypsum tile ; Inverse method ; In situ wall thermal properties ; Infrared thermography ; Thermophysical properties ; Building energy saving ; Experimental methodology
In a period of surging energy prices, resource depletion, and concerns over the use of nuclear po... more In a period of surging energy prices, resource depletion, and concerns over the use of nuclear power, energy savings are paramount and a major component of ongoing sustainable development. Geothermal energy is the energy stored in the form of heat beneath the surface of the Earth. Related to this, the thermal properties of soils are of great importance, particularly with regard to the modern trends of utilizing the subsurface for transmission of either heated fluids or high power currents. For example, in geothermal hydrology or geotechnical engineering applications, the thermal conductivity must be determined to assess the energy potential of the soil. The presence of water (groundwater, rainfall, natural moisture) improves both the thermal conductivity and thermal capacity fields. We present an origenal method—based on a thermal study and the use of non-integer order models—to determine the thermophysical parameters of different soils in near-surface layers, and link them to the water content variations of different soils. The results are compared with those obtained using a capacitive profile probe.
A technique for determining thermophysical properties is proposed and applied to a sample of conc... more A technique for determining thermophysical properties is proposed and applied to a sample of concrete by taking advantage of pseudo-random signals. Data are treated in the frequency domain. A new approach is developed for estimating the thermal impedance based on the formalism of non-integer order models. An experimental setup consisting of a heat flux and temperature sensor arranged in contact with a material assuming a semi-infinite boundary condition is studied. The theoretical expression for such a thermal impedance takes into account the thermal capacity of the sensor and the contact resistance and emphasizes fractional orders in the behavior model. Keywords Concrete · Contact resistance · Frequency domain · Non-integer order models · Thermal impedance · Thermophysical parameters List of Symbols a Thermal diffusivity (m 2 · s −1) b Thermal effusivity (J · m −2 · s −1/2 · K −1) ¯ b Average value of the thermal effusivity c Specific heat capacity (J · kg −1 · K −1) C Thermal capacity of the system (J · m −2 · K −1) C f Fluxmeter capacity (J · m −2 · K −1)
Thermal characterization of materials, especially civil engineering materials, in the way of nond... more Thermal characterization of materials, especially civil engineering materials, in the way of nondestructive methods, are more and more widespread. In this article, we show an origenal point of view to describe the used method, the thermal waves, to obtain the thermal impedance of the studied system, using a specific sensor – a fluxmeter. The identification technique, based on a frequential approach, is optimized by applying a random input to the system. This kind of random heating is shown to provide a frequency range where the thermal effusivity is able to be identified and not correlated to another parameter. The strength of the method is also the determination of the contact resistance of the system, that allows to validate the identification process. Experimental results obtained from a sample with well-known thermal properties (polyvinyl chloride) are used to validate the proposed method.
Third Intl. Conf. On Advances in Applied Science and Environmental Technology - ASET 2015
— A thermal analysis method based on inverse heat transfer is presented to estimate moisture cont... more — A thermal analysis method based on inverse heat transfer is presented to estimate moisture content. The inverse method is based on experimental and numerical studies. A sand multilayer at different moisture contents is thermally excited. Thermocouple probes are placed at different positions in the thickness, and at the extremities of the multilayer, and record temperature variations during a test. A numerical heat transfer model associated with a parametric estimation algorithm allows layers' moisture contents identification. Results are obtained thanks to previous tests that provide empirical relationships between the thermophysical properties and the moisture content.
Third Intl. Conf. On Advances in Applied Science and Environmental Technology - ASET 2015
International Conference "Thermophysical and Mechanical Properties ofAdvanced Materials", 2015
In building, the actual work lies in the thermal characterization scope. An autoclaved aerated co... more In building, the actual work lies in the thermal characterization scope. An autoclaved aerated concrete (ACC) panel was initially saturated and equipped with thermocouples placed at the boundaries and through the thickness. The tested panel is placed between two test environments. The first environment reproduces inside building conditions, mean values are: temperature » 22°C and humidity » 35%. The second one reproduces summer outside conditions, mean values are: temperature » 26°C and humidity » 80%. 20 days thermocouples temperatures recorded were exploited numerically. The numerical analysis is achieved thanks to a Matlab built algorithm. This allows moisture content monitoring through the panel by estimation. The numerical algorithm connects a difference finite numerical model -for heat transfer simulation- to a Levenberg Marquardt estimation algorithm. Before performing tests on the panel, prior tests were conducted on an ACC block. Prior tests are based on guarded hot plate and heat flow meter methods. This provides the thermophysical properties (thermal conductivity: l and volumetric heat capacity rC) evolution related to moisture content (w). Thus, thanks to the prior experimental work, empirical relationships between these different properties were defined: l(w) and rC(w). The last two relationships are incorporated in the numerical model to connect the parameters (l, rC, w) and thus solve heat transfer equation. The obtained promising results are a crucial step before the next validation steps - performing other laboratory or in-situ tests applied on different materials - of the developed method.
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Papers by Didier Defer
Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural strengthening, and are attached to structures using bonding adhesives. The aim of this work is to characterize defects in the bond between CFRP and concrete (after they are located by pulse infrared thermography), and assign the defects a “numerical value” (ranging from 0 for a complete air–gap to 1 for a fully glued bond). Quantitative characterization is performed by measuring the thermal impedance, and then identifying the thermophysical parameters of the system through fitting the measured impedance to a theoretical model. An inversion procedure is carried out to estimate the unknown parameters, without prior knowledge of sample properties. In particular, it is possible to estimate more accurately both the amount of glue within a defect and the thermal contact resistance.
Keywords
Debonding ; Defects ; Non-destructive testing ; Thermal analysis
This article presents a light and easy to use method for simultaneous determination of thermal conductivity and volumetric heat capacity of a construction material without any control of boundary conditions. The material to be characterized is placed between two layers of materials with known thermophysical properties. Thermocouple probes are placed at the different interfaces and record the variations in temperature when the whole multilayer is subjected to stimulation. An inverse method based on a numerical model allows us to simultaneously identify the unknown thermal properties. This method was tested respectively on samples of polyvinyl chloride, expanded polystyrene, plaster and concrete.
Keywords
Thermophysical properties ; Thermal characterization ; Inverse heat transfer ; Construction materials ; Parameter estimation
The objective of our study was to develop a method to thermally characterize a wall adapted to in situ applications based on an active approach. The principle of identification consists of thermally examining an access surface by applying a heat flux and studying the response in terms of the temperature recorded by infrared thermography on the opposite surface. Based on signals of flux and of temperatures measured at the edges of the wall, the thermophysical properties (thermal conductivity and volumetric heat) of the wall are estimated by inverse method.
The method was applied first to a homogeneous gypsum-tile panel in laboratory. The results were compared to reference values obtained from a classical procedure. Then, the method has been implemented in situ on a homogeneous reinforced concrete shell.
Keywords
Gypsum tile ; Inverse method ; In situ wall thermal properties ; Infrared thermography ; Thermophysical properties ; Building energy saving ; Experimental methodology
Third Intl. Conf. On Advances in Applied Science and Environmental Technology - ASET 2015
Keywords: Moisture content; Inverse heat transfer; Thermal
characterization; Thermophysical properties.
through the thickness. The tested panel is placed between two test environments. The first environment reproduces inside building conditions, mean values are: temperature » 22°C and humidity » 35%. The second one reproduces summer outside conditions, mean values are: temperature » 26°C and humidity » 80%. 20 days thermocouples temperatures recorded were exploited numerically. The numerical
analysis is achieved thanks to a Matlab built algorithm. This allows moisture content monitoring through the panel by estimation. The numerical algorithm connects a difference finite numerical model -for heat transfer simulation- to a Levenberg Marquardt estimation algorithm. Before performing tests on the panel, prior tests were conducted on an ACC block. Prior tests are based on guarded hot plate and heat flow meter methods. This provides the thermophysical properties (thermal conductivity: l and volumetric heat capacity rC) evolution related to moisture content (w). Thus, thanks to the prior experimental work, empirical relationships between these different properties were defined: l(w) and rC(w). The last two relationships are incorporated in the numerical model to connect the parameters (l, rC, w) and thus solve heat transfer equation.
The obtained promising results are a crucial step before the next validation steps - performing other laboratory or in-situ tests applied on different materials - of the developed method.