VALIDATION D'UN CODE DE TRANSFERT DE CHALEUR ET D'HUMIDITÉ DANS UNE PAROI SELON LA NORME EN 15026

International audienceLa simulation numérique des transferts de masse et de chaleur est devenue un outil important pour l'étude du comportement des parois d'un bâtiment que ce soit pour évaluer les performances de différents éléments constitutifs ou pour déterminer l'évolution globale d'un bâtiment dans son environnement. Devant le développement croissant des modèles mis en oeuvre pour ces simulations numériques, la norme EN15026 permet de préciser les équations à mettre en oeuvre pour le calcul du transfert d'humidité et de chaleur en régime instationnaire ainsi que leurs conditions d'utilisation. Cette norme propose également un exemple de référence destiné à valider un modèle numérique. Cet article présente le modèle numérique développé au laboratoire, nommé TMC et montre qu'il répond aux exigences de cette norme

Validation d'un modèle numérique 1D de transfert de masse et de chaleur

National audienceDans le cadre de la caractérisation hygrothermique de matériaux à faible qualité environnementale, un modèle numérique unidimensionnel de transfert de masse et de chaleur nommé TMC a été mis au point au laboratoire. Ce modèle est actuellement en cours de validation. Cet article présente d'une part le modèle numérique développé et le compare, d'autre part, à une solution analytique et à d'autres modèles existants sur un cas test simple fourni par la littérature. Celui-ci consiste à modéliser la distribution d'humidité sur un mur homogène sous conditions isothermes en 1D. Initialement, le mur est en équilibre avec les ambiances intérieures et extérieures. A t>0, les ambiances sont modifiées. La distribution d'humidité au sein du mur à 100 h, 300 h et 1000 h est alors étudiée. ABSTRACT. In the context of hygrothermical caracterization of environmental friendly materials, a numerical model, called TMC, for describing mass and heat transfer is developed in our laboratory. This paper presents at first the numerical unidimensionnal model and secondly, compares it to analytical solution and other models on a simple test case. This case consists in modelling humidity distribution in homogenous wall under isothermal conditions. Initialy, the wall is in equilibrium with indoor and outdoor surroundings. Then, conditions are modified and humidity distribution in a wall at 100 h, 300 h and 1000 h is studied

Effect of coating on the hygric performance of a hemp concrete wall

International audienceConstructions built with environmentally friendly materials like hemp concrete know currently a real development thanks to their low environmental impact and their interesting thermo-hydric properties. Their porous structure presents lots of advantages in terms of life quality compared with usual concretes. An experimental facility is designed to measure temperature and relative humidity within a hemp concrete wall (30 cm thick) submitted to climatic solicitations. This facility provides a set of experimental data suited for benchmarking a 1D HAM model. In the present work, the wall is submitted to relative humidity gradient under almost isothermal conditions. Comparisons between numerical and experimental data are performed. The results indicate that the use of main wetting curve is suited to describe the storage capacity of the material. However the use of hysteresis modelling is able to improve the description of drying stages. The hydro-thermal properties of the same wall coated on one side with traditional hemp lime render are then investigated numerically. The coating effect on relative humidity distributions is analysed. The ability of the coating to regulate moisture is pointed out

MODELISATION DU TRANSFERT D'AIR, DE MASSE ET DE CHALEUR AUX TRAVERS DE PAROIS MULTICOUCHES

Les constructions à faible impact environnemental à structure poreuse connaissent actuellement un véritable essor. Le développement de modèles numériques capables de prévoir leur comportement hygrothermique s'avère être un outil précieux. Le modèle développé traite des échanges de masse, de chaleur et d'air au sein de matériaux poreux dans différentes configurations et soumis à des conditions climatiques diverses. Au travers de cinq cas tests numériques issus d'un benchmark international HAMSTAD, un modèle de calcul développé sous COMSOL Multiphysics est présenté. Ce logiciel de calcul par éléménts finis est adapté à la résolution de systèmes d'équations différentielles fortement couplées appliqués à des structures multicouches et multidimensionnelles rencontrées dans l'enveloppe des bâtiments. La cohérence des résultats obtenus pour les cas tests nous permet de valider notre modèle

Modélisation du transfert de chaleur et de masse : impact de la perméabilité à l'air et de l'hystérésis pour le béton de chanvre

National audienceIn the context of hygrothermical caracterization of environmentally friendly materials, a non hysteretic 1D model, for describing mass and heat transfer is implemented with COMSOL. The model is validated thanks to an international benchmark HAMSTAD WP2. Numerical and experimental results from hemp concrete wall submitted to real climatic solicitations are compared. The poor agreement between these one conducts to analyse the air transfer through the wall and the modeling of sorption isotherm hysteresis

Influence of temperature on sorption process in hemp concrete

International audienceHemp concrete is a bio-based material which is currently undergoing a growing development. Its hygrothermal behaviour highly depends on the evolution of the moisture content which has a significant influence on heat and moisture transfer. Hysteresis phenomenon and temperature effects on sorption process make difficult the prediction of the moisture content evolution. Hysteresis phenomenon determines the equilibrium moisture content during successive adsorption/desorption cycles. Temperature influences also the equilibrium moisture content: the warmer the temperature, the lower will be the equilibrium moisture content at the same relative humidity. These two phenomena are most often neglected for modelling the moisture content evolution in heat and moisture transfer models. This can cause significant discrepancies to predict the hygrothermal response of a material subjected to climatic variations. This paper intents to contribute to the better knowledge of such sorption processes by providing new measurements and by analysing and comparing different theoretical approaches. Some adsorption and desorption main and intermediate scanning curves are measured at two different temperatures. Models taking into account these phenomena are presented. The comparison between experimental and numerical results shows that the theoretical approaches investigated are promisin

Hygrothermal behaviour of a hemp concrete wall : influence of sorption isotherm modelling

International audienceConstructions built with environmentally friendly materials like hemp concrete know currently a real development. The development of numerical models able to evaluate their hygrothermal behaviour turns out to be a precious tool for their study. The model deals with coupled heat, mass and air transfer through multi-layer 1D porous media submitted to climatic variations. The model is used to simulate the behaviour of a hemp concrete wall. Comparison between simulation and experiment is done showing the importance of taking into account hysteresis for sorption isotherm modelling

Hygrothermal transfers through a bio-based multilayered wall: Modeling study of different wall configurations subjected to various climates and indoor cyclic loads

The hygrothermal behavior of a bio-based multilayered wall has been studied by numerical simulations. The key point of these research investigations was to properly describe the hygrothermal transfers occurring inside the studied wall solution. In previous work, the case of the wall subjected to a given real climate (Wroughton HIVE demonstrator, UK, Feb 2018) has been investigated. The present work, focused on the moisture regulation capacity of the wall, considers an improved kinetics model of sorption, different layer configurations, one additional climate (Bordeaux, FR, Apr 2008) and the effect of indoor cyclic loads. Compared to the classical approach, the local kinetics approach results in prediction of stronger and steeper hygric dynamics with larger relative humidity variations at small time scales. The study of the different wall configurations allows to determine the best one in terms of moisture damping: the vapor control membrane is advantageously removed provided the OSB3 12 mm layer is replaced by an OSB4 18 mm layer. Moreover, the simulations show that the Moisture Buffer Value characteristic of each material layer is not a sufficient criterion to evaluate hygric performance of the wall; strong hygric interactions occur with the layer’s permeability independently of its sorption capacity. Finally, water content hysteresis phenomena are studied and it appears that under usual operating conditions, they can be ignored by adjusting the layers’ permeabilities for adequate fits on the Moisture Buffer Value tests

Hygrothermal transfers through a bio-based multilayered wall: Modeling study of different wall configurations subjected to various climates and indoor cyclic loads

International audienceThe hygrothermal behavior of a bio-based multilayered wall has been studied by numerical simulations. The key point of these research investigations was to properly describe the hygrothermal transfers occurring inside the studied wall solution. In previous work, the case of the wall subjected to a given real climate (Wroughton HIVE demonstrator, UK, Feb 2018) has been investigated. The present work, focused on the moisture regulation capacity of the wall, considers an improved kinetics model of sorption, different layer configurations, one additional climate (Bordeaux, FR, Apr 2008) and the effect of indoor cyclic loads. Compared to the classical approach, the local kinetics approach results in prediction of stronger and steeper hygric dynamics with larger relative humidity variations at small time scales. The study of the different wall configurations allows to determine the best one in terms of moisture damping: the vapor control membrane is advantageously removed provided the OSB3 12 mm layer is replaced by an OSB4 18 mm layer. Moreover, the simulations show that the Moisture Buffer Value characteristic of each material layer is not a sufficient criterion to evaluate hygric performance of the wall; strong hygric interactions occur with the layer's permeability independently of its sorption capacity. Finally, water content hysteresis phenomena are studied and it appears that under usual operating conditions, they can be ignored by adjusting the layers' permeabilities for adequate fits on the Moisture Buffer Value tests

APOL1 C-Terminal Variants May Trigger Kidney Disease through Interference with APOL3 Control of Actomyosin

The C-terminal variants G1 and G2 of apolipoprotein L1 (APOL1) confer human resistance to the sleeping sickness parasite Trypanosoma rhodesiense, but they also increase the risk of kidney disease. APOL1 and APOL3 are death-promoting proteins that are partially associated with the endoplasmic reticulum and Golgi membranes. We report that in podocytes, either APOL1 C-terminal helix truncation (APOL1Δ) or APOL3 deletion (APOL3KO) induces similar actomyosin reorganization linked to the inhibition of phosphatidylinositol-4-phosphate [PI(4)P] synthesis by the Golgi PI(4)-kinase IIIB (PI4KB). Both APOL1 and APOL3 can form K+ channels, but only APOL3 exhibits Ca2+-dependent binding of high affinity to neuronal calcium sensor-1 (NCS-1), promoting NCS-1-PI4KB interaction and stimulating PI4KB activity. Alteration of the APOL1 C-terminal helix triggers APOL1 unfolding and increased binding to APOL3, affecting APOL3-NCS-1 interaction. Since the podocytes of G1 and G2 patients exhibit an APOL1Δ or APOL3KO-like phenotype, APOL1 C-terminal variants may induce kidney disease by preventing APOL3 from activating PI4KB, with consecutive actomyosin reorganization of podocytes.info:eu-repo/semantics/publishe