Moisture Transport Model for Enhancing FHWA HIPERPAV Predictions

2009 ◽  
Vol 2113 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Qinwu Xu ◽  
J. Mauricio Ruiz ◽  
George K. Chang ◽  
Robert O. Rasmussen ◽  
Dan K. Rozycki
Keyword(s):  
Moisture Transport ◽  
Transport Model

Moisture Transport in Wood-Based Structural Panels under Transient Hygroscopic Conditions

2020 ◽  
Vol 70 (3) ◽  
pp. 283-292
Author(s):  
Daniel Way ◽  
Frederick A. Kamke ◽  
Arijit Sinha
Keyword(s):  
Moisture Transport ◽  
Transport Model ◽  
Oriented Strand Board ◽  
Primary Objective ◽  
Accelerated Weathering ◽  
Wood Composite ◽  
Transport Parameters ◽  
Moisture Profile ◽  
Cyclic Changes ◽  
Wood Based Composite

Abstract Development of moisture gradients within wood and wood-based composites can result in irreversible moisture-induced damage. Accelerated weathering (AW), generally employing harsh environmental conditions, is a common tool for assessing moisture durability of wood composite products. Use of milder AW conditions, such as cyclic changes in relative humidity (RH), may be of interest to the wood-based composites industry in assessing moisture durability under more realistic conditions. The primary objective of this study was to determine whether moisture profile development in oriented strand board and plywood during cyclic RH changes could be reasonably predicted with a simple moisture transport model, which may be practical for wood-based composite industry members seeking to develop new AW protocols. The diffusion model based on Fick's second law with empirically determined moisture transport parameters fits the experimental data reasonably well for the purpose of screening RH parameters.

Influence of Cultivar on the Predictive Performance of a Moisture Transport Model Developed for Parboiled Paddy Drying

2013 ◽  
Vol 31 (5) ◽  
pp. 494-506 ◽  
Author(s):  
Lovelyn N. Onuoha ◽  
Ndubisi A. Aviara ◽  
Toyin A. Abdulrahim ◽  
Ahmed T. Suleiman
Keyword(s):  
Moisture Transport ◽  
Transport Model ◽  
Predictive Performance

Non-isothermal Moisture Transport calculations with DIM 3.1 / Nicht-isotherme Berechnungen des Feuchtigkeitstransportes mit Hilfe des Porgrammes DIM 3.1

2000 ◽  
Vol 6 (4) ◽  
pp. 367-384
Author(s):  
J. Grunewald ◽  
R. Plagge
Keyword(s):  
Water Vapour ◽  
Liquid Water ◽  
Balance Equation ◽  
Constitutive Equations ◽  
Moisture Transport ◽  
Moisture Transfer ◽  
Transport Model ◽  
Transport Coefficients ◽  
Equation System ◽  
Transport Processes

Abstract The application of a general thermodynamical mass and energy transport model to the coupled heat and moisture transfer in porous materials results in a balance equation system and the related constitutive equations of the considered quantities. The constitutive equations describe moisture transport in a phase-separated manner leading into phase-divided hygric transport coefficients (liquid water permeability, water vapour diffusivity). A conceptual model is presented in the paper in order to circumvent the difficulties resulting from non-isothermal overlaying moisture transport processes. Since phase-divided hygric transport coefficients are not directly measurable, but moisture transport coefficients in distinct hygric ranges, moisture conductivities and a phase dividing function are introduced. The moisture conductivities include liquid water and water vapour transport. For a known phase dividing function, the phase-divided hygric transport coefficients of the balance equation system can be calculated from the measurable moisture conductivities. The influence of a variation of the introduced phase-dividing function on non-isothermal moisture transport processes is investigated by means of computer simulations.

scholarly journals Modeling Anomalous Moisture Transport in Cement-Based Materials with Kinetic Permeability

2020 ◽  
Vol 21 (3) ◽  
pp. 837 ◽  
Author(s):  
Zhidong Zhang ◽  
Ueli Angst
Keyword(s):  
Moisture Transport ◽  
Transport Model ◽  
Weibull Function ◽  
Cement Pastes ◽  
Dimensional Changes ◽  
Proposed Model ◽  
Cement Based Materials ◽  
Moisture State ◽  
Conventional Models ◽  
Good Agreement

The durability of reinforced concrete structures is closely related to moisture state in cement-based materials. Therefore, it is crucial to develop moisture models that can accurately predict moisture state in the materials. However, many studies reported anomalous moisture transport in cement-based materials that cannot be well simulated by the conventional models. Several reasons have been investigated in the literature, such as the complex pore structure, chemical reactions with water, dimensional changes of the tested specimen, etc. Nevertheless, only a few models are able to capture the anomaly of moisture transport. This study viewed the main moisture transport coefficient—permeability—as a kinetic variable that depends on both the degree of moisture saturation and the contact time. The time-dependence was formulated by the decay (for drying) or growth (for wetting) functions. The saturation-dependence was calculated by the van Genuchten–Mualem (VGM) model. These functions were then implemented into a moisture transport model that was developed in previous studies. The proposed model was validated by experimental data and showed a good agreement for cement pastes that were dried or wetted in the hygroscopic range. Numerical simulation results were also compared with the simplified solutions to a fractional derivative model (FDM) of anomalous diffusion and the empirical Weibull function. We found that the solutions to the FDM cannot provide appropriate results. Weibull function performs as well as the proposed model, but the empirical function lacks physical meanings.

A revised multi-Fickian moisture transport model to describe non-Fickian effects in wood

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 563-572 ◽  
Author(s):  
Henrik Lund Frandsen ◽  
Lars Damkilde ◽  
Staffan Svensson
Keyword(s):  
Diffusion Equation ◽  
Transport System ◽  
Moisture Transport ◽  
Transport Model ◽  
Bound Water ◽  
Anomalous Behavior ◽  
Adsorption Rate ◽  
Fickian Diffusion ◽  
Sorption Rate ◽  
Rate Model

Abstract This paper presents a study and a refinement of the sorption rate model in a so-called multi-Fickian or multi-phase model. This type of model describes the complex moisture transport system in wood, which consists of separate water vapor and bound-water diffusion interacting through sorption. At high relative humidities, the effect of this complex moisture transport system becomes apparent, and since a single Fickian diffusion equation fails to model the behavior, it has been referred to as non-Fickian or anomalous behavior. At low relative humidities, slow bound-water transport and fast sorption allow a simplification of the system to be modeled by a single Fickian diffusion equation. To determine the response of the system, the sorption rate model is essential. Here the function modeling the moisture-dependent adsorption rate is investigated based on existing experiments on thin wood specimens. In these specimens diffusion is shown to be negligible, allowing a separate study of the adsorption rate. The desorption rate has been observed to be slower at higher relative humidities as well, and an expression analogous to the adsorption rate model is proposed. Furthermore, the boundary conditions for the model are discussed, since discrepancies from corresponding models of moisture transport in paper products have been found.

scholarly journals Untersuchung von Feuchtetransport mittels numerischer Modellierung und Neutronentransmissionsanalyse / Study of Moisture Transport by Numerical Modeling and Neutron Transmission Analysis

1997 ◽  
Vol 3 (4) ◽  
pp. 355-370
Author(s):  
H. Pleinert ◽  
H. Sadouki ◽  
F.H. Wittmann
Keyword(s):  
Moisture Transport ◽  
Building Materials ◽  
Transport Model ◽  
Neutron Radiography ◽  
High Sensitivity ◽  
Moisture Distribution ◽  
Transfer Model ◽  
Porous System ◽  
Neutron Transmission ◽  
Good Spatial Resolution

Abstract Moisture transport in porous building materials is described by a transport model that expresses the action of the several transport mechanisms of liquid water and water vapor in the porous system by a single material specific transfer coefficient. This parameter has to be determined by experimental measurement of moisture distributions inside samples exposed to known initial and boundary conditions. Neutron radiography is employed as experimental method because of its high sensitivity and good spatial resolution. The moisture distribution is determined from the raw data obtained in the measurement by a calculation procedure based on a signal transfer model of the neutron transmission. This approach is illustrated by two examples: the drying of a plain brick sample and the drying of a composite sample consisting of two brick elements separated by a layer of mortar.

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