References of "Dubois, Samuel"
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See detailNon-isothermal moisture balance equation in porous media: a review of mathematical formulations in Building Physics
Dubois, Samuel ULg; Lebeau, Frédéric ULg; Evrard, Arnaud ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (in press)

Understanding heat and mass transfers in porous materials is crucial in many areas of scientific research. Mathematical models have constantly evolved, their differences lying mainly in the choice of the ... [more ▼]

Understanding heat and mass transfers in porous materials is crucial in many areas of scientific research. Mathematical models have constantly evolved, their differences lying mainly in the choice of the driving potentials used to describe moisture flows, as well as in the complexity of characterizing the physical phenomena involved. Models developed in the field of Building Physics (HAM models) are used to describe the behavior of envelope parts and assess their impact on user comfort and energy performance. The water balance equation can be described in many ways; it is a function of the boundary conditions considered and the fact they induce high or low water content in the porous materials used. This paper gives an overview of various formulations for this equation that are found in the Building Physics literature. It focuses first on the physically based formulation of moisture balance, drawing on the Representative Elementary Volume (REV) concept, coupled with thermodynamic flow rates description. This is then reformulated in line with various main moisture state variables offering a wide variety of expressions that are compared with available models. This approach provides access to all secondary transport coefficients associated with the process of mathematical transformation. Particular emphasis is placed on the moisture storage function choice and its impact on the final mathematical formulations. [less ▲]

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See detailAn inverse modelling approach to estimate the hygric parameters of clay-based masonry during a Moisture Buffer Value test
Dubois, Samuel ULg; McGregor, Fionn; Evrard, Arnaud et al

in Building & Environment (2014), 81

This paper presents an inverse modelling approach for parameter estimation of a model dedicated to the description of moisture mass transfer in porous hygroscopic building materials. The hygric behaviour ... [more ▼]

This paper presents an inverse modelling approach for parameter estimation of a model dedicated to the description of moisture mass transfer in porous hygroscopic building materials. The hygric behaviour of unfired clay-based masonry samples is specifically studied here and the Moisture Buffer Value (MBV) protocol is proposed as a data source from which it is possible to estimate several parameters at once. Those include materials properties and experimental parameters. For this purpose, the mass of two clay samples with different compositions is continuously monitored during several consecutive humidity cycles in isothermal conditions. Independently of these dynamic experimental tests, their moisture storage and transport parameters are measured with standard steady-state methods. A simple moisture transfer model developed in COMSOL Multiphysics is used to predict the moisture uptake/release behaviour during the MBV tests. The set of model parameters values that minimizes the difference between simulated and experimental results is then automatically estimated using an inverse modelling algorithm based on Bayesian techniques. For materials properties, the optimized parameters values are compared to values that were experimentally measured in steady state. And because a precise understanding of parameters is needed to assess the confidence in the inverse modelling results, a sensitivity analysis of the model is also provided. [less ▲]

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See detailModeling the hygrothermal response of a prefabricated straw bale panel and assessing its impact on indoor climate
Dubois, Samuel ULg; Evrard, Arnaud; Lebeau, Frédéric ULg

in 2014 ASABE and CSBE/SCGAB Annual International Meeting (2014, July)

Crop-based materials show many qualities in the quest for construction products with low environmental impact in the construction sector. Their ability to exchange moisture with indoor air offers new ... [more ▼]

Crop-based materials show many qualities in the quest for construction products with low environmental impact in the construction sector. Their ability to exchange moisture with indoor air offers new opportunities for improving interior user comfort and eventually buildings energy performance. Modeling their hygrothermal behavior has thus focused much attention, one of the main objectives being to assess more objectively the resulting performance at building scale. The first natural step in this modeling process is to understand the specific dynamics of heat and mass transfer within such materials. The Building Element Heat Air and Moisture (BEHAM) numerical models were designed to accurately predict internal conditions encountered in materials with partial balance equations. This envelope-based approach, however, requires the knowing of the interior and exterior climate conditions prior to the study. Therefore, it forbids any assessment of mutual exchange between the envelope to the indoor air and prevents any serious validation of the overall performance of materials. In response to this problem, the importance of developing whole building hygrothermal model has recently been raised. General scientific computational tools like MATLAB seem particularly adapted to perform this scaling-up, given their high flexibility and tools integration potentialities. In this communication we study a prefabricated straw bale panel subjected to two distinct and simple solicitations in a climatic chamber. A whole building hygrothermal model developed in MATLAB is then validated with the experimental datasets. The evolution of indoor conditions under the different tests is analyzed in details with an assessment of straw bales performance. [less ▲]

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See detailImpact des matériaux biosourcés sur le climat intérieur : Un outil de calcul flexible à l'échelle de la pièce
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Conference (2014, March 19)

L'impact de l'utilisation de matériaux d'origine végétale sur le climat intérieur, et donc sur le confort des occupants ainsi que la performance énergétique du bâtiment, n'est établi que partiellement ... [more ▼]

L'impact de l'utilisation de matériaux d'origine végétale sur le climat intérieur, et donc sur le confort des occupants ainsi que la performance énergétique du bâtiment, n'est établi que partiellement. Ces produits présentent des propriétés hygroscopiques et capillaires causant des phénomènes spécifiques liés aux changements de phase dynamiques au sein de la matrice poreuse. Les modèles mathématiques utilisés pour étudier leur comportement hygrothermique de manière détaillée sont souvent des modèles de paroi (dits modèles HAM - Heat Air Moisture). Cela sous-tend qu'ils nécessitent d'imposer des conditions aux limites à toutes les frontières de l'élément étudié, et ne permettent donc pas de connaître les flux de chaleur et de masse réels qu'offrent l'assemblage de matériaux vers le volume d'air intérieur. Pour y accéder, il convient d'intégrer ces modèles à la description de bilans thermique et hydrique de zones. Dans cette communication, nous présentons un modèle hygrothermique capable de simuler l'évolution temporelle du climat intérieur d'une ou de plusieurs pièces ("zones thermiques"). Il est composé d'un module HAM basé sur des équations aux dérivées partielles et caractérisant les transferts dans les matériaux de construction et développé au sein de l'environnement numérique COMSOL Multiphysics. Les équations qui le composent sont flexibles et facilement adaptables au cas expérimental modélisé ainsi qu'aux propriétés des matériaux composant les parois. En outre, on y trouve un traitement complet des phénomènes de changement de phase qui prend en compte l'impact de la température sur la capacité de stockage d'humidité du matériau. Ce premier module, est couplé à un outil caractérisant les bilans chaleur/masse au niveau de la zone à l'aide d'équations aux dérivées ordinaires. Le couplage des modèles est effectué au sein de SIMULINK, un outil de MATLAB destiné à l'étude des systèmes dynamiques. Nous appliquons ensuite ce modèle à l'étude d'un mur en ballots de paille séparant une enceinte climatique de grande taille en deux volumes d'air. Les données d'une expérience simple, un choc thermique imposé à un des volumes d'air, sont comparées aux sorties du modèle numérique. [less ▲]

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See detailDesign, Construction and Validation of a Guarded Hot Plate Apparatus for Thermal Conductivity Measurement of High Thickness Crop-Based Specimens
Dubois, Samuel ULg; Lebeau, Frédéric ULg

in Materials and Structures (2013)

The search for sustainability achievement in the building sector led to the use of crop-based insulation materials. Among these, raw products like plant straws bales can present elementary representative ... [more ▼]

The search for sustainability achievement in the building sector led to the use of crop-based insulation materials. Among these, raw products like plant straws bales can present elementary representative volumes (REVs) in the size order of several square centimeters. Fibers orientation may play an important role on material thermal behavior. Measuring their thermal conductivities with standard steady-state equipment can thus lead to some inaccuracies due to the necessity of resetting lower thickness samples. This paper presents a Guarded Hot Plate (GHP) apparatus designed to test high thickness samples, up to 40cm, with an accuracy of 2%. The different parts of the machine are described in details along with design process and challenges encountered. Temperature and heat flux measurements in the device represent critical design stages where optimal accuracy is needed in order to optimize the resulting global error. Regarding this, necessary numerical and experimental analyzes were conducted emphasizing on intrinsic systematic error assessment. To complete the study, some validations tests are performed on a reference material and other widely-spread polystyrene slabs. These tests take into account the optimal computation parameters resulting from the numerical analysis and the apparatus proved to be in accordance with accuracy requirements. [less ▲]

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See detailModeling the hygrothermal behavior of biobased construction materials
Dubois, Samuel ULg; Evrard, Arnaud; Lebeau, Frédéric ULg

in Journal of Building Physics (2013)

Materials with high moisture exchange capacity may have a strong impact on indoor climate conditions as well as building energy performance. Crop-based materials, characterized by their high porosity and ... [more ▼]

Materials with high moisture exchange capacity may have a strong impact on indoor climate conditions as well as building energy performance. Crop-based materials, characterized by their high porosity and hygroscopicity, belong to this category. Modeling their hygrothermal behavior accurately is thus particularly relevant for appropriate building design. A COMSOL Multiphysics transient heat air and moisture model is developed in this article to simulate moisture exchange between a lime–hemp concrete block and surrounding air during a Moisture Buffer Value evaluation test. Results are then compared with the validated heat air and moisture software using performance criteria showing a slight preference for both moisture exchanges and latent heat effect characterization. It offers yet additional advantages in terms of flexibility and transparency as well as further evolution potential. [less ▲]

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See detailHygrothermal behavior modeling of different Lime-Hemp Concrete mixes
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Conference (2013, May 28)

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied ... [more ▼]

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied, varying the type of binder. First Moisture Buffer Value determination tests are lead experimentally using the NORDTEST protocol. These dynamic experiments, which reveal the moisture storage and exchange capacity together with latent heat effects, are then modeled using a set of partial differential equations. The reduction of humidity buffering capacity induced by hydraulic binder incorporation is properly evaluated and the hygrothermal parameters can be assessed by inverse modeling. [less ▲]

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See detailMoisture equilibrium in straw bale walls
Evrard, Arnaud; Louis, Arnaud ULg; Biot, Benjamin et al

Conference (2012, November)

Straw bales technology for buildings is developing in Belgium as in many other countries. The market is growing but significant uncertainties are left concerning how to model its dynamical hygrothermal ... [more ▼]

Straw bales technology for buildings is developing in Belgium as in many other countries. The market is growing but significant uncertainties are left concerning how to model its dynamical hygrothermal performances and its long term behaviour. The present paper presents the preliminary analysis conducted on material parameters and component’s response to dynamic heat and moisture solicitations. The simulations use WUFI Pro software based on material parameters form literature and both reference climate files for Belgium and theoretical climates to analyse the interactions between straw bale walls and finishing materials and their influence on component performances and durability. A specific prefabricated wall element sold on Belgian market is detailed and introduced in simulations. The influence on comfort feelings and indoor air quality are discussed with a focus on component´s thermal inertia and moisture regulation capacity. The paper concludes with recommendations on wall composition to help straw bale technologies to develop in building market of Belgium and other countries. [less ▲]

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See detailHygrothermal modelling of Lime-Hemp concrete used as building material and indoor climate buffering characterization
Dubois, Samuel ULg; Evrard, Arnaud; Lebeau, Frédéric ULg

Poster (2012)

Hygroscopic building materials can affect the indoor air by exchanging moisture with it and buffering the ambient humidity variations. The Nordtest protocol and the concomitant Moisture Buffer Value (MBV ... [more ▼]

Hygroscopic building materials can affect the indoor air by exchanging moisture with it and buffering the ambient humidity variations. The Nordtest protocol and the concomitant Moisture Buffer Value (MBV) parameter definition has been one of the first attempt to characterize this moisture regulation performance. This paper present an attempt to confront this well-established experimental protocol with a mathematical model implemented in the Comsol multiphysics solver. The power of the simulation will be showed with a good correlation between the modelling and the experimental phase for the MBV determination of a lime-hemp concrete bloc. [less ▲]

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See detailÉtude de la distribution granulométrique de particules de chanvre: Méthodes par tamisage et analyse d'image
Dubois, Samuel ULg; Lebeau, Frédéric ULg

Report (2011)

Ce document présente une analyse de la répartition granulométrique d'une chènevotte commerciale. Deux techniques différentes sont étudiées. La première consiste à séparer les particules mécaniquement par ... [more ▼]

Ce document présente une analyse de la répartition granulométrique d'une chènevotte commerciale. Deux techniques différentes sont étudiées. La première consiste à séparer les particules mécaniquement par tamisage. La diversité morphologique des particules de chanvre entraîne cependant des questions quant à l'interprétation des résultats obtenus, et plus particulièrement sur les paramètres physiques réellement discriminatoires dans cette séparation en classes granulométriques. Il est montré ici que l'analyse d'image permet de répondre à cette question et d'apporter des informations précieuses dans la description des particules. A cette fin, la performance de descripteurs issus d'algorithmes de calcul en analyse d'image est étudiée. Enfin, une représentation multi-classes de la distribution granulométrique de la chènevotte est proposée, regroupant les descriptions dimensionnelle et morphologique des particules. [less ▲]

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See detailConception et instrumentation d'un bâtiment prototype en ballots de paille
Dubois, Samuel ULg

Master's dissertation (2010)

Le pavillon Africasylves constitue un projet de construction durable, réalisé au sein de la Faculté de Gembloux. Ce bâtiment a deux facettes bien distinctes : l’information, en offrant une application ... [more ▼]

Le pavillon Africasylves constitue un projet de construction durable, réalisé au sein de la Faculté de Gembloux. Ce bâtiment a deux facettes bien distinctes : l’information, en offrant une application concrète de concepts écologiques et pouvant démontrer leur bien-fondé au plus grand nombre, et la recherche scientifique. Son étude vise en effet à mettre en évidence les réponses concrètes que les techniques de construction en paille peuvent apporter face à la crise environnementale et la remise en cause profonde des pratiques du secteur du bâtiment. Le texte commence par définir les notions développées, comme le bâtiment durable, les matériaux écologiques et le projet de démonstration. On trouve ensuite une analyse bibliographique de la construction en paille, destinée à mettre en avant les conditions d’une bonne mise en œuvre. La suite du texte est consacrée à la conception du pavillon et aux études préliminaires. Le suivi de la mise en œuvre et des recommandations achèvent l’étude de ce projet. [less ▲]

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