Materials Science and Engineering Commons^™

Finite Volume Numerical Analysis Of The Thermal Property Of Cellular Concrete Based On Two And Three Dimensional X-Ray Computerized Tomography Images, She Wei, Yang Yonggan, Xie Deqing, Zhang Yunsheng

International Conference on Durability of Concrete Structures

Cellular concrete is one kind of lightweight concrete, which are widely used in thermal insulation engineering project. In this study, a three dimensional (2D and 3D) finite-volume-based models was developed for analyzing the heat transfer mechanisms through the porous structures of cellular concretes under steady-state heat transfer condition and also for investigating the differences between 2D and 3D modeling results. 2D and 3D reconstructed pore networks were generated from the microstructural information measured by a 3D image captured by X-ray computerized tomography (X-CT). In addition, the 3D-computed value of the effective thermal conductivity was found to be in better agreement ...

On Utilization Of Elliptical Rings In Assessing Cracking Tendency Of Concrete, Xiangming Zhou, Olayinka G. Oladiran, Wei Dong

International Conference on Durability of Concrete Structures

A new experimental method by utilizing elliptical rings to replace circular rings recommended by ASTM and AASHTO was explored for assessing cracking potential of concrete and other cement-based materials under restrained condition. A series of thin and thick elliptical concrete rings were tested alongside circular ones until cracking. Cracking age, position, and propagation were carefully examined. It is found that thin elliptical rings with appropriate geometry can initiate cracks quicker than circular ones, which is desirable for accelerating the ring test. However, thick elliptical rings seem not to exhibit a desirable geometry effect of accelerating ring test compared with circular ...

The Correlation Of Chloride Diffusion Coefficient And Concrete Maturity Value And Its Application In Hong Kong–Zhuhai–Macao Bridge Engineering, Pengping Li, Shengnian Wang, Jianbo Xiong, Rui Chai, Yu Yan

International Conference on Durability of Concrete Structures

The correlation of chloride diffusion coefficient and concrete maturity value within 56 days of curing was investigated by the chemically combined water content method, rapid chloride migration (RCM) test, and concrete maturity test. The experimental results showed that chloride diffusion coefficient of concretes decreased not only with increasing curing ages but also with increasing curing temperature, which can promote the hydration degree of cementitous materials. There is a significant correlation between the chloride diffusion coefficient of indoor cured specimens and the concrete maturity value when expressed as a power function (R₂ = 0.976). In addition, the calculated values of ...

Influence Of Controlled Permeability Formwork On The Permeability Of Concrete, Wei Lin, Q. Jiang, J. Liu, J. Liu

International Conference on Durability of Concrete Structures

Corrosion of steel reinforcement related to the intrusion of chloride ion is still the main threats to the durability of concrete structure, especially in marine environment. For the purpose of delaying the Cl⁻ concentration at the surface of steel reinforcement reaching the critical value leading to initial corrosion, the permeability of concrete is usually improved by optimizing the concrete mixture to achieve high compatibility as well as optimized pore structure. In recent years, controlled permeability formwork (CPF) which was originally developed to obtain much smoother surface of the concrete proves to promote the service performance of the concrete by enhancing ...

Opto-Electronic Devices With Nanoparticles And Their Assemblies, Chieu Van Nguyen

Chemical & Biomolecular Engineering Theses, Dissertations, & Student Research

Nanotechnology is a fast growing field; engineering matters at the nano-meter scale. A key nanomaterial is nanoparticles (NPs). These sub-wavelength (< 100nm) particles provide tremendous possibilities due to their unique electrical, optical, and mechanical properties. Plethora of NPs with various chemical composition, size and shape has been synthesized. Clever designs of sub-wavelength structures enable observation of unusual properties of materials, and have led to new areas of research such as metamaterials. This dissertation describes two self-assemblies of gold nanoparticles, leading to an ultra-soft thin film and multi-functional single electron device at room temperature. First, the layer-by-layer self-assembly of 10nm Au nanoparticles and polyelectrolytes is shown to behave like a cellular-foam with modulus below 100 kPa. As a result, the composite thin film (~ 100nm) is 5 orders of magnitude softer than an equally thin typical polymer film. The thin film can be compressed reversibly to 60% strain. The extraordinarily low modulus and high compressibility are advantageous in pressure sensing applications. The unique mechanical properties of the composite film lead to development of an ultra-sensitive tactile imaging device capable of screening for breast cancer. On par with human finger sensitivity, the tactile device can detect a 5mm imbedded object up to 20mm below the surface with low background noise. The second device is based on a one-dimensional (1-D) self-directed self-assembly of Au NPs mediated by dielectric materials. Depending on the coverage density of the Au NPs assembly deposited on the device, electronic emission was observed at ultra-low bias of 40V, leading to low-power plasma generation in air at atmospheric pressure. Light emitted from the plasma is apparent to the naked eyes. Similarly, 1-D self-assembly of Au NPs mediated by iron oxide was fabricated and exhibits ferro-magnetic behavior. The multi-functional 1-D self-assembly of Au NPs has great potential in modern electronics such as solid state lighting, plasma-based nanoelectronics, and memory devices.

Adviser: Ravi F. Saraf

Infrared Transmitting Glasses With High Glass Transition Temperatures, Steve W. Martin

Iowa State University Patents

A chalcogenide glass capable of infrared transmission which is either sulfur, selenium or tellurium based and consists of compositions of the formula MX+M.sub.2 'X.sub.3 +SiX.sub.2, wherein M is one of the metals calcium, strontium, barium, zinc and lead, and M' is either aluminum or gallium and X is either sulfur, selenium or tellurium. Aluminum or gallium chalcogenide acts to increase the covalent bonding network structure of the glass with the result being that excellent high temperature 8-14 micron IR transmitting glasses with transition temperatures above 500C are prepared.

Use Of Liquid Pressure-Pulse Decay Permeameter In Experimental Evaluation Of Permeability In Wellbore Cement Under Geopressured Geothermal Conditions, Kolawole Bello, Mileva Radonjic

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

Geopressured reservoirs in the northern Gulf of Mexico basin along the coast of Louisiana have been determined to be viable source of geothermal energy and potential sites for carbon sequestration, where CO2 can be utilized to induce convective flow of geofluids and enhance heat harvesting. These reservoirs are made of unconsolidated sandstone capped by shale layers and possess temperatures as high as 140⁰C. At high temperatures, cement strength retrogression occur when calcium silicate hydrate phase in hydrated cement converts to alpha dicalcium silicate hydrate phase. The higher the temperature, the quicker the rate of transformation of calcium silicate hydrate. The ...

Numerical Solution Of Burgers' Equation Arising In Longitudinal Dispersion Phenomena In Fluid Flow Through Porous Media By Crank-Nicolson Scheme, Ravi Borana, Vikas Pradhan, Manoj Mehta

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The present paper discusses the numerical solution of the Burgers’ equation arising in longitudinal dispersion phenomenon in fluid flow through porous media. In the porous medium pure water, salt water or contaminated water disperse in longitudinal direction gives rise to a non-linear partial differential equation in the form of Burgers’ equation. The equation is solved by using Crank-Nicolson finite difference scheme with appropriate initial and boundary conditions. The longitudinal dispersion phenomenon may be miscible or immiscible fluid flow through porous media. The problem of miscible displacement can be seen in the coastal areas, where fresh water beds are gradually displaced ...

Evaporation From A Capillary Tube: Experiment And Modelization, Emmanuel Keita, Pamela Faure, Stephane Rodts, Phillippe Coussot, David Weitz

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

Drying is known to play a major role in soils and buildings materials. Better understanding the physics may help saving cost and energy. Thus control of the drying kinetics is a key factor. In permeable porous media, capillary forces lead to constant curvature of the air/water interface. The value of the curvature and the shape of the interface depend strongly on the pore geometry. Thus small change in their shape may lead to main change of the air/water interface as the medium desaturates. As the surface is supplied with water the drying rate remains at a constant value ...

Experimental Study For Air Cooling Using Membrane Covered Tray, Mohamed Ali, Obida Zeitoun, Hany Al-Ansary, Abdullah Nuhait

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

An experimental study is conducted to cool the outdoor air using a humidification technique. A wind tunnel was built with a membrane covered tray serves as a test section. An outdoor air passes over a tray full of water and covered with a specific membrane. Air temperatures and relative humidity are measured before and after the tray for several air and water speeds. Air speed is measured at different locations along the centerline of the cross section. Results show that as the angle of the tray increases the air temperature drop increases which improve the efficiency of the humidification technique ...

Keynote Talk – Novel Convective Heat Transfer Enhancement In Channels And Tubes Filled With Nanofluid-Saturated Metal Foams, Fumika Sakai, Wenhao Li, Akira Nakayama

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

A local thermal non-equilibrium theory was exploited to investigate heat transfer in nanofluid saturated porous media, in view of possible heat transfer applications of metal foams filled with nanofluids as high performance heat exchangers. The resulting set of the macroscopic equations based on the modified Buongiorno model proposed by Yan et al. for convective heat transfer in nanofluids were used to obtain the analytical solutions for laminar fully developed forced convection in channels and tubes filled with nanofluid saturated metal foams. The analytical and numerical solutions were obtained for laminar fully developed forced convection in channels and tubes filled with ...

Influence Of Thermal Radiation From Solid Phase Upon The Local Thermal Non-Equilibrium Condition In A Porous Medium, Yasser Mahmoudi, Nader Karimi

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

Present work investigates numerically the effect of thermal radiation from solid phase on the fluid and solid temperature fields inside a porous medium through investigating forced convection heat transfer process within a pipe filled with a porous media. A local thermal non-equilibrium (LTNE), two-equation model is employed to represent the energy transport for the solid and fluid phases. The radiative heat transfer equation is solved by discrete ordinate method (DOM) to compute the radiative heat flux in the porous medium. The effects of radiative heat transfer from solid phase on the temperature profiles of the solid and fluid phases are ...

Heat Flow From A Buried Cylindrical Tank Partially Submerged In Groundwater, Robert Mckibbin, Shigeo Kimura

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

This study was motivated by the possibility of re-use of buried cylindrical tanks, once a facility for fuel storage at motor vehicle service stations (now relinquished by oil companies), but remaining for use as thermal reservoirs connected to space heating systems (e.g. for convenience stores) in Japan. The ground in which a tank is buried is assumed to be of uniform porosity and permeability, with a phreatic groundwater surface (water table) that may rise and fall, albeit slowly, over time. The ground and the water are subject to heating and cooling according to the season and weather conditions. Here ...

Investigation Of Transpiration Cooling With Local Thermal Non-Equilibrium Model: Effects Of Different Thermal Boundary Conditions At The Porous-Fluid Interface, Zheng Huang, Yin-Hai Zhu, Pei-Xue Jiang, Yan-Bin Xiong

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

In this study, the main stream coupled with a porous medium with local thermal non-equilibrium assumption is analyzed. The flow inside the porous material is modelled using the Darcy–Brinkman–Forchheimer equation and the incompressible Navier-Stokes equations are solved for the main stream. Several couple conditions between the main flow temperature and the temperatures of the solid matrix and coolant flow at the fluid/porous interface is calculated. The results show that the Model C assumes the main flow temperature equals the solid phase temperature and the main flow heat flux is all imposed on the solid phase gives the ...

Effective Permeability Upscaling From Heterogenous To Homogenous Porous Media, Mehmet Cicek, Deepak Devegowda, Faruk Civan, Richard Sigal

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

An effective method to upscale permeability is presented to represent a heterogeneous reservoir with homogeneous permeability and porosity values. As a result, there is no need to deal with dual-porosity or dual-permeability models in reservoir simulations. Thus, the required CPU time for reservoir production and flow simulations is reduced significantly.

Pressure Transient Characteristics Of Multi-Stage Fractured Horizontal Wells In Shale Gas Reservoirs With Consideration Of Multiple Mechanisms, Jingjing Guo, Liehui Zhang, Haitao Wang

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The approach of multi-stage fractured horizontal wells (MFHWs) has been proven an efficient technology for successful development of shale gas reservoirs. Together with multiple gas flow mechanisms, the existence of multiple hydraulic fractures further complicates the gas flowing problem in shale gas reservoirs. Understanding pressure transient dynamics of MFHWs in shale gas reservoirs is of great importance to provide a perception into long-term pressure dynamics forecast as well as to estimate relevant reservoir and fracturing parameters. This paper presents a comprehensive seepage model to investigate the characteristics of pressure transient responses of a horizontal well intercepted by multiple finitely conductive ...

Modified Rhie-Chow / Piso Algorithm For Collocated Variable Finite Porous Media Flow Solvers, Markus Nordlund

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

A modified Rhie-Chow/ PISO segregated algorithm is proposed, whic by construction avoids the development of spurious oscillations in the solution fields for low Mach number flow in heterogeneous, isotropic porous media. The collocated variable finite volume based algorithm modifies the commonly used Rhie-Chow interpolation to maintain a strong pressure-velocity coupling when large discontinuous implicit momentum sources are present. This Redistributed Resistivity PISO algorithm is based on a redistribution of the flow resistivity over the neighboring grid cells to the discontinuity. The proposed algorithm is successfully verified against published data for the velocity and pressure for two cases. The robustness of ...

Turbulence In Porous Media: Some Fundamental Questions Addressed By Dns Solutions, Marc Florian Uth, Y. Jin, H. Herwig

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

In a generic porous matrix built by a large number of rectangular bars the flow is determined numerically by a DNS approach. Turbulent flow is thus simulated avoiding modelling in order to decide whether turbulent structures with scales much larger than the pore scale exist. So far only under-resolved DNS solutions are determined from which, however, definite conclusions with respect to the maximum turbulent length scale can be drawn.

Wall Thickness Optimization Of A Transpiration-Cooled Sharp Leading Edge At Atmospheric Re-Entry, Christian Dittert

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

The purpose of this paper is to find the necessary cooling mass flow for a defined wall thickness distribution, which allows a selective cooling for an acceptable temperature range of the sharp leading edge of an atmospheric re-entry vehicle. Due to the angle of attack during the re-entry flight the pressure at the top side is lower than the pressure at the bottom side. However, the highest heat load occurs at the stagnation point at which also the maximum pressure is effective. The efficiency of a transpiration cooling depends on the mass flow rate of the coolant. The cooling mass ...

Numerical Solutions Of Non-Linear Fractional Transport Models In Unconventional Hydrocarbon Reservoirs Using Variational Iteration Method, Nadeen Malik, Iftikhar Ali, Bilal Chanane

5th International Conference on Porous Media and Their Applications in Science, Engineering and Industry

Unconventional hydrocarbon reservoirs, such as, shale gas deposits, offer a new source of energy resources. These reservoirs consist of tight porous rocks which are characterized by nano-scale size porous networks with ultra-low permeability. The mathematical modeling of phenomena through such tight porous media provides its own challenges. In this study, we consider a relatively new approach by modeling the transport of gas by the time-fractional advection-diffusion equation,