J. M. P. Q. Delgado

Transport Processes in Porous Media

Fundamentals of Porous Structures.- Flow in Porous Media.- Transport Phenomena in Porous Structures.- Modeling of Transport Processes in Porous Materials.- Experimental Investigation of Transport in Porous Media.- Applications & Examples.- Conclusions & Recommendations.

Measurement of the coefficient of transverse dispersion in flow through packed beds for a wide range of values of the schmidt number

Experimental values of the coefficient of transverse dispersion (DT) were measured with the system 2-naphthol/water, over a range of temperatures between 293K and 373K, which corresponds to a range of values of viscosity (μ) between 2.83×10−4 Ns/m2 and 1.01×10−3 Ns/m2 and of molecular diffusion coefficient (Dm) between 1.03×10−9 m2/s and 5.49×10−9 m2/s. Since the density (ρ) of water is close to 103 kg/m3, the corresponding variation of the Schmidt number (Sc=μ/ρDm) was in the range 1000 – 50. More than 200 experimental values of the transverse dispersion coefficient were obtained using beds of silica sand with average particle sizes (d) of 0.297 and 0.496mm, operated over a range of interstitial liquid velocities (u) between 0.1mm/s and 14mm/s and this gave a variation of the Reynolds number (Re=ρduε/μ) between 0.01 and 3.5.Plots of the dimensionless coefficient of transverse dispersion (DT/Dm) vs. the Peclet number (Pem=ud/Dm) based on molecular diffusion bring into evidence the influence of Sc on transverse dispersion. As the temperature is increased, the value of Sc decreases and the values of DT/Dm gradually approach the line corresponding to ‘gas behaviour’ (i.e. Sc ≈ 1), which is known to be well approximated by the equation DT/Dm=1/τ+ud/12Dm, where τ is the tortuosity with regard to diffusion.

Numerical Analysis of Heat and Mass Transfer in Porous Media

Numerical Analysis of Mass Transfer around a Sphere Buried in Porous Media: Concentration Contours and Boundary Layer Thickness.- Unsaturated-Saturated Flow in Porous Media under Centrifugation.- Applying Computational Analysis in Studies of Resin Transfer Moulding.- Mass Transport in Growing Porous Media.- Modeling the Pore Level Fluid Flow in Porous Media using the Immersed Boundary Method.- Computer Simulation of Nanoparticles Deposition.- A Comparison of Thermal Dispersion Behaviour in High-Conductivity Porous Media of Various Pore Geometries.- Assessment of Heat Affected Zone of Submerged Arc Welding Process through Digital Image Processing.- Study of diffusion in a one-dimensional lattice-gas model of zeolites: The analytical approach and kinetic Monte Carlo simulations.- Contaminant transport in partially saturated porous.- Three-dimensional diffusion in arbitrary domain using generalized coordinates for the boundary condition of the first kind.- Convection and heat transfer of viscoelastic fluids saturated a porous medium.- Unsteady Heat Conduction from Spheroids.

Can moisture buffer performance be estimated from sorption kinetics

This article describes the research on the moisture buffering effect of building materials. A set of experiments on samples of current building materials are conducted under transient conditions of relative humidity (RH). The results obtained are then analyzed using kinetics models. The experimental settings are based on the moisture buffer value (MBV) test method currently under study by Nordic researchers. The main result from these tests is the MBV number that can be used to characterize the moisture buffer performance of a material or a system. The application of kinetics models to the experimental results is explored and several parameters are retrieved. A proposal for the use of these parameters is presented and its practical use is discussed.

Application of Data Mining Techniques

In this chapter, the data mining techniques described in chapter 3 are applied to the case study described in chapter 4. The overcome of the difficulties associated with the analysis process of the data using appropriate techniques is demonstrated.

Numerical Simulation of the Vibration Behavior of Curved Carbon Nanotubes

Several zigzag and armchair single-walled carbon nanotubes (CNTs) were modeled by a commercial finite element package and their vibrational behavior was studied. Numerous computational tests with different boundary conditions and different bending angles were performed. Both computational and analytical results were compared. It was shown that the computational results are in good agreement with the analytical calculations in the case of straight tubes. In addition, it was concluded that the natural frequency of straight armchair and zigzag CNTs increases by increasing the chiral number of both armchair and zigzag CNTs. It was also revealed that the natural frequency of CNTs with higher chirality decreases by introducing bending angles. Nevertheless, the influence of increasing bending angle on the natural frequency of armchair and zigzag CNTs with lower chiral number is almost negligible.

Analysis and Monitoring of the Drying Process of a Hygro-Regulated Wall Base Ventilation System Implemented in a Historical Church to Control Rising Damp

Treating rising damp in the walls of historic buildings is a very complex procedure and the traditional techniques currently used to minimize rising damp are not effective or too expensive, in particular when dealing with walls of considerable thickness and heterogeneous materials. This work presents the results of an in situ application of the hygro-regulated wall base ventilation system to control rising damp in a historical church located in northern Portugal. The main purpose is to validate the wall base ventilation technology for treating rising damp in very thick and heterogeneous walls. The analytical model used well describes the observed features of rising damp in building walls, verified by in-field tests, which contributed to simple sizing of the hygro-regulated wall base ventilation system to be implemented in historical buildings.

Impact of MG2+ and tara gum concentrations on flow and textural properties of WPI solutions and cold-set gels.

Cold-set gels of whey protein isolate (WPI) and of WPI plus tara gum (TG) were produced through the addition of magnesium chloride to heat-denatured (HD) WPI and WPI+TG solutions. The flow behaviour of the WPI, TG, and WPI+TG samples was analyzed: WPI solutions exhibit Newtonian behavior while the behavior of the TG and WPI+TG solutions can be described through the Cross and Carreau models. The mechanical characterization of the cold-set gels was done through puncture tests, and the Youngs modulus for each cold-set gel was obtained. Statistical analysis of the mechanical data was made according to the Marquadt-Levenberg algorithm.

Salt Damage and Rising Damp Treatment in Building Structures

Salt damage can affect the service life of numerous building structures, both historical and contemporary, in a significant way. In this review, various damage mechanisms to porous building materials induced by salt action are analyzed. The importance of pretreatment investigations is discussed as well; in combination with the knowledge of salt and moisture transport mechanisms they can give useful indications regarding treatment options. The methods of salt damage treatment are assessed then, including both passive techniques based on environmental control, reduction of water transport, or conversion to less soluble salts and active procedures resulting in the removal of salts from deterioration zones. It is concluded that cellulose can still be considered as the favorite material presently used in desalination poultices but hydrophilic mineral wool can serve as its prospective alternative in future applications. Another important cause of building pathologies is the rising damp and, in this phenomenon, it is particularly severe considering the presence of salts in water. The treatment of rising damp in historic building walls is a very complex procedure and at Laboratory of Building Physics (LFC-FEUP) a wall base hygroregulated ventilation system was developed and patented.

Heat and mass transfer in porous media

Treatment of Rising Damp in Historical Buildings.- The Evaluation of Hygroscopic Inertia and Its Importance to the Hygrothermal Performance of Buildings.- Two-phase flow and heat transfer in micro-channels and their applications in micro-system cooling.- Numerical Methods for Flow in Fractured Porous Media.- Lungs as a Natural Porous Media: Architecture, Airflow Characteristics and Transport of Suspended Particles.- On Analogy between Convective Heat and Mass Transfer Processes in a Porous Medium and a Hele-Shaw Cell.- Heat and Mass Transfer in Porous Materials with Complex Geometry: Fundamentals and Applications.- Contribution to Thermal Properties of Multi-Component Porous Ceramic Materials used in High-Temperature Processes in the Foundry Industry.- Metal Foams Design for Heat Exchangers: Structure and Effectives Transport Properties.- Heat and Mass Transfer in Matrices of Hygroscopic Wheels.