The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Patrick Perré - One of the best experts on this subject based on the ideXlab platform.
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On the importance of heat and Mass transfer coupling for the characterization of hygroscopic insulation materials
International Journal of Heat and Mass Transfer, 2019Co-Authors: Patrick Perré, Arnaud Challansonnex, Julien ColinAbstract:This work is focused on Mass transfer characterization of hygroscopic materials used for insulation, such as low density fiberboards (LDF). Due to their particular morphology, these panels present a very high Mass Diffusivity due to the connected gaseous phase together with a very low thermal conductivity. This combination of properties exacerbates the coupling between heat and Mass transfer in transient state. Based on experimental data obtained with an original set-up and relevant simulations performed using a comprehensive physical formulation, a throughout vision of this question is proposed in the present study. In particular, we emphasize on: - The impressive change in core temperature in terms of magnitude and duration, - The great impact of the internal temperature gradient, which slows down Mass diffusion, - The dramatic error on Mass Diffusivity value if the coupling is ignored, - The possible determination of thermal conductivity during transient sorption tests. A dimensionless number Nc was derived to quantify the intensity of this coupling. Finally, a practical example is proposed that confirms the importance of heat and Mass transfer coupling in the case of LDF, and at the same time, proves that this effect can be controlled and corrected by using a relevant physical formulation.
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On the importance of heat and Mass transfer coupling for the characterization of hygroscopic insulation materials
2018Co-Authors: Patrick Perré, Arnaud ChallansonnexAbstract:The present work is focused on Mass transfer characterization of hygroscopic materials used for insulation, such as Low Density Fibreboards. Due to their particular morphology, these panels present a very high Mass Diffusivity in the connected gaseous phase and a very low thermal conductivity. This combination of properties exacerbates the coupling between heat and Mass transfer in transient state. Based on experimental data obtained with an original set-up and relevant simulations performed using a comprehensive physical formulation, a throughout vision of this question is proposed in the present study. In particular, we emphasize on: - The impressive change in core temperature in terms of magnitude and duration, - The great impact of the internal temperature gradient, which slows down Mass diffusion, - The dramatic error on Mass Diffusivity value if the coupling is ignored.
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On the importance of heat and Mass transfer coupling during characterization of hygroscopic insulation materials
Proceedings of 21th International Drying Symposium, 2018Co-Authors: Patrick Perré, Arnaud ChallansonnexAbstract:The present work is focused on Mass transfer characterization of hygroscopic materials used for insulation, such as Low Density Fibreboards. Due to their particular morphology, these panels present a very high Mass Diffusivity in the connected gaseous phase and a very low thermal conductivity. This combination of properties exacerbates the coupling between heat and Mass transfer in transient state. Based on experimental data obtained with an original set-up and relevant simulations performed using a comprehensive physical formulation, a throughout vision of this question is proposed in the present study. In particular, we emphasize on: - The impressive change in core temperature in terms of magnitude and duration, - The great impact of the internal temperature gradient, which slows down Mass diffusion, - The dramatic error on Mass Diffusivity value if the coupling is ignored.
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Heat and moisture diffusion in spruce and wood panels computed from 3-D morphologies using the Lattice Boltzmann method
International Journal of Thermal Sciences, 2018Co-Authors: M. Louërat, M. Ayouz, Patrick PerréAbstract:In this paper, the Lattice Boltzmann method is used to simulate heat and Mass diffusion in bio-based building materials. The numerical method is presented and the methodology developed to reduce the calculation time is described. The 3-D morphologies of spruce and wood fibers are obtained using synchrotron X-ray micro-to-mography. Equivalent macroscopic properties (heat conductivity and Mass Diffusivity) are therefore determined from the real micro-structure of the materials. The results reveal the anisotropy of the studied materials. The computed equivalent heat conductivity varies from − − 0.036 W m K 1 1 to − − 0.52 W m K 1 1 and the computed di-mensionless Mass Diffusivity varies from 0.0088 to 0.78 depending on the materials and on the diffusion directions. Using these results, morphology families are identified and simple expressions are proposed to predict the equivalent properties as a function of phase properties and solid fraction.
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Mass Diffusivity determination of various building materials based on inverse analysis of relative humidity evolution at the back face of a sample
Construction and Building Materials, 2018Co-Authors: Arnaud Challansonnex, Floran Pierre, Joel Casalinho, Patrick PerréAbstract:Abstract In this study, we use a novel method to determine the Mass diffusion coefficients of hygroscopic materials. The experiment involves subjecting one face of the sample to relative humidity (RH) variations over time and measuring the RH at the back face. The imposed RH and temperature are measured during the experiment, and they are used as boundary conditions in a comprehensive computational code to address heat and Mass transfer in porous media. This new method is utilized to characterize the following building materials: autoclave aerated concrete, plaster, poplar wood, pine wood, medium-density fiberboard and low-density fiberboard. This paper provides the details regarding the determination of the sorption isotherms of the selected materials that are required for the determination of Mass Diffusivity. The obtained electrical tortuosity values are compared with geometrical tortuosity values determined via microtomography and three-dimensional image processing. The agreement between the two tortuosity values is applicable only for porous media with narrow pore size distribution.
Romain Rémond - One of the best experts on this subject based on the ideXlab platform.
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Characterization of sorption behavior and Mass transfer properties of four central africa tropical woods: Ayous, Sapele, Frake, Lotofa
MADERAS: Ciencia y Tecnología, 2016Co-Authors: Merlin Simo-tagne, Romain Rémond, Yann Rogaume, André Zoulalian, Patrick PerréAbstract:This study provides the sorption isotherm, its hysteresis and their Mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia Superba), lotofa (Sterculia Rhinopetala), sapele (Entandrophragma Cylindricum) and ayous (Triplochiton Scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40 degrees C with air relative humidity ranged from 0% to 90%. Mass Diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and Mass transfer properties were determined in the tangential direction with a "false'' quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model's explains plausibly the experimental sorption isotherms data. Results on characterization of Mass transfer properties showed that, in the steady state, Mass Diffusivity decreases exponentially when basal density increases. Mass Diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and Mass Diffusivity.
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Characterization of sorption behavior and Mass transfer properties of four central africa tropical woods: Ayous, Sapele, Frake, Lotofa
Maderas. Ciencia y tecnología, 2016Co-Authors: Merlin Simo-tagne, Romain Rémond, Yann Rogaume, André Zoulalian, Patrick PerréAbstract:International audienceThis study provides the sorption isotherm, its hysteresis and their Mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia Superba), lotofa (Sterculia Rhinopetala), sapele (Entandrophragma Cylindricum) and ayous (Triplochiton Scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40 degrees C with air relative humidity ranged from 0% to 90%. Mass Diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and Mass transfer properties were determined in the tangential direction with a "false'' quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model's explains plausibly the experimental sorption isotherms data. Results on characterization of Mass transfer properties showed that, in the steady state, Mass Diffusivity decreases exponentially when basal density increases. Mass Diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and Mass Diffusivity
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Characterization of sorption behavior and Mass transfer properties of four central africa tropical woods: Ayous, Sapele, Frake, Lotofa
Maderas-ciencia Y Tecnologia, 2016Co-Authors: Merlin Simo-tagne, Romain Rémond, Yann Rogaume, André Zoulalian, Patrick PerréAbstract:This study provides the sorption isotherm, its hysteresis and their Mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia Superba), lotofa (Sterculia Rhinopetala), sapele (Entandrophragma Cylindricum) and ayous (Triplochiton Scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40°C with air relative humidity ranged from 0% to 90%. Mass Diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and Mass transfer properties were determined in the tangential direction with a ‘’false’’ quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model’s explains plausibly the experimental sorption isotherms data. Results on characterization of Mass transfer properties showed that, in the steady state, Mass Diffusivity decreases exponentially when basal density increases. Mass Diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and Mass Diffusivity.
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moisture diffusion coefficient of reaction woods compression wood of picea abies l and tension wood of fagus sylvatica l
Wood Science and Technology, 2012Co-Authors: Asghar Tarmian, Hadi Dashti, Romain Rémond, Patrick PerréAbstract:The moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture Diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small Mass Diffusivity in compression wood. In contrast, the Mass Diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers).
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Moisture diffusion coefficient of reaction woods: compression wood of Picea abies L. and tension wood of Fagus sylvatica L.
Wood Science and Technology, 2011Co-Authors: Asghar Tarmian, Hadi Dashti, Romain Rémond, Patrick PerréAbstract:International audienceThe moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture Diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small Mass Diffusivity in compression wood. In contrast, the Mass Diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers)
Asghar Tarmian - One of the best experts on this subject based on the ideXlab platform.
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moisture diffusion coefficient of reaction woods compression wood of picea abies l and tension wood of fagus sylvatica l
Wood Science and Technology, 2012Co-Authors: Asghar Tarmian, Hadi Dashti, Romain Rémond, Patrick PerréAbstract:The moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture Diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small Mass Diffusivity in compression wood. In contrast, the Mass Diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers).
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Moisture diffusion coefficient of reaction woods: compression wood of Picea abies L. and tension wood of Fagus sylvatica L.
Wood Science and Technology, 2011Co-Authors: Asghar Tarmian, Hadi Dashti, Romain Rémond, Patrick PerréAbstract:International audienceThe moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture Diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small Mass Diffusivity in compression wood. In contrast, the Mass Diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers)
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Mass transfer in medium density fiberboard (MDF) modified by Na+ montmorillonite (Na+MMT) nanoclay
Maderas. Ciencia y tecnología, 2011Co-Authors: Reza Zahedsheijani, Asghar Tarmian, Hadi Gholamiyan, Hossein YousefiAbstract:The potential use of nanoclay was examined to modify fluid transfer properties of medium density fiberboard (MDF). For this, Na+ montmorillonite (Na+MMT) nanoclay was added to urea formaldehyde resin to produce MDF. Then, the air permeability and Mass Diffusivity of MDF were evaluated. Scanning electron microscope (SEM) images and X-ray diffraction (XRD) confirmed a dispersion and exfoliation of Na+MMT in the modified MDF. The air permeability presented a systematic decrease with increasing nanoclay amount. This reduction agreed with the simple ‘‘tortuous path’’ model. The nanoclay had no effect on the Mass Diffusivity.
Hadi Dashti - One of the best experts on this subject based on the ideXlab platform.
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moisture diffusion coefficient of reaction woods compression wood of picea abies l and tension wood of fagus sylvatica l
Wood Science and Technology, 2012Co-Authors: Asghar Tarmian, Hadi Dashti, Romain Rémond, Patrick PerréAbstract:The moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture Diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small Mass Diffusivity in compression wood. In contrast, the Mass Diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers).
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Moisture diffusion coefficient of reaction woods: compression wood of Picea abies L. and tension wood of Fagus sylvatica L.
Wood Science and Technology, 2011Co-Authors: Asghar Tarmian, Hadi Dashti, Romain Rémond, Patrick PerréAbstract:International audienceThe moisture diffusion coefficient of compression wood in spruce (P. abies) and tension wood in beech (F. sylvatica) was examined. The results indicated that the diffusion coefficient measured under steady-state condition (cup method) could well characterize the drying kinetics of the reaction woods. The compression wood offered more resistance to the moisture Diffusivity when compared with the corresponding normal wood. The thick cell wall rich in lignin explains the small Mass Diffusivity in compression wood. In contrast, the Mass Diffusivity in beech is almost always higher in tension wood than in normal wood, in spite of similar density values. The high moisture diffusion in tension wood can be explained by the ease of bound water diffusion in the gelatinous layers (G-layers)
Jung-yang San - One of the best experts on this subject based on the ideXlab platform.
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measurement of apparent solid side Mass Diffusivity of a water vapor silica gel system
International Journal of Heat and Mass Transfer, 2002Co-Authors: Jung-yang SanAbstract:Abstract A measurement of the apparent solid-side Mass Diffusivity of water vapor adsorbed in a regular density silica gel is performed by using a constant-pressure thermal gravimetrical apparatus. The diameter of the silica gel particles is 2 mm. Six adsorption isotherms, individually correspond to 5.1, 22.2, 34.3, 49.5, 64.4 and 79.6 °C, are measured. The covered range of moisture content is from 0% to 40%. Using a previously developed model, which considers both surface (film) heat and Mass transfer resistances, the measured uptake curves yield the apparent solid-side Mass diffusivities. The apparent solid-side Mass Diffusivity is expressed as a function of temperature and moisture content. The thermal effect and importance of surface Mass transfer resistance are individually discussed.
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Measurement of apparent solid-side Mass Diffusivity of a water vapor–silica gel system
International Journal of Heat and Mass Transfer, 2002Co-Authors: Jung-yang SanAbstract:Abstract A measurement of the apparent solid-side Mass Diffusivity of water vapor adsorbed in a regular density silica gel is performed by using a constant-pressure thermal gravimetrical apparatus. The diameter of the silica gel particles is 2 mm. Six adsorption isotherms, individually correspond to 5.1, 22.2, 34.3, 49.5, 64.4 and 79.6 °C, are measured. The covered range of moisture content is from 0% to 40%. Using a previously developed model, which considers both surface (film) heat and Mass transfer resistances, the measured uptake curves yield the apparent solid-side Mass diffusivities. The apparent solid-side Mass Diffusivity is expressed as a function of temperature and moisture content. The thermal effect and importance of surface Mass transfer resistance are individually discussed.
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Validity of solid-side Mass Diffusivity in simulation of water vapor adsorbed by silica gel in packed beds
International Journal of Thermal Sciences, 2002Co-Authors: Jung-yang San, Sheng-hsiang HsuAbstract:Abstract Three different sets of solid-side Mass Diffusivity are individually used in simulation of the heat and Mass transfer in a silica gel packed bed. The packed bed is installed at the exit of a fixed-bed dehumidification system to dampen the periodical moisture fluctuation. One of the three sets of solid-side Mass Diffusivity is experimental data. The other two, individually with a tortuosity factor (τs) of 1.0 and 2.8, are theoretical results in an Arrhenius form. The variations of air temperature and humidity ratio at the inlet and outlet of the packed bed are measured. The measured data match well with the simulation results obtained by using the measured D. The three sets of solid-side Mass Diffusivity are also individually used in simulation of the heat and Mass transfer in a packed-bed dehumidification system in which the silica gel particles experience with a significant cyclic temperature variation. The validity of the two theoretical solid-side Mass diffusivities is discussed for various operating conditions. The comparison shows that the computer simulation with τs of 1.0 predicts the processes more accurate than that with τs of 2.8 does.