This study discusses results of experiments on hydrodynamic assessment of gas flow through backbone (skeletal) porous materials with an anisotropic structure. The research was conducted upon materials of diversified petrographic characteristics – cokes. The study was conducted for a variety of hydrodynamic conditions, using air. The basis for assessing hydrodynamics of gas flow through porous material was a gas stream that results from the pressure forcing such flow. The results of measurements indicate a clear impact of the type of material on the gas permeability, and additionally – as a result of their anisotropic internal structure – to a significant effect of the flow direction on the value of gas stream. In aspect of scale transfer problem, a method of mapping the flow geometry of skeletal materials has been developed and usefulness of numerical methods has been evaluated to determine pressure drop and velocity distribution of gas flow. The results indicate the compliance of the used calculation method with the result of experiments.
Moulding properties of Isasa River Sand bonded with Ipetumodu clay (Ife-North Local Government Area, Osun State, Nigeria) were investigated. American Foundry men Society (AFS) standard cylindrical specimens 50mm diameter and 50mm in height were prepared from various sand and clay ratios (between 18% and 32%) with 15% water content. The stress-strain curves were generated from a universal strength testing machine. A flow factor was calculated from the inclination of the falling slope beyond the maximum compressive strength. The result shows that the flowability of the samples increases from 18% to 26% clay content, its maximum value was attained at 26% and then it decreases from 30% to 32% clay content. The green compressive strength, dry compressive strength and air permeability values obtained from the mould samples were in accordance with standard values used in foundry practice. The x-ray diffraction test shows that the sand contains silicon oxide (SiO2), Aluminium oxide (Al2O3), and Aluminium silicate (Al6Si2O13). The mould samples were heated to a temperature of 1200 o C to determine the sintering temperature; fussion did not take place at this temperature. The results showed that the sand and clay mixture can be used to cast ferrous and non-ferrous alloys.
The study was aimed to determine the hydrodynamic of water seepage through a porous bed saturated with different amounts of high viscosity liquids. An attempt was made to describe the process of seepage through beds saturated with oils using the theory of outflow of a liquid from the tank. It was assumed that the discharge coefficient will represent changes of flow resistance during the process. It was found that the dependence of this factor on time is linear. In the second part of this work kinetics of the seepage process was investigated. Dependence of oil concentrations, eluted from the deposit with the flowing water, on time has been evaluated. Thanks to these studies it was possible to determine the effectiveness of an elution of high viscosity liquids from porous beds using water as the washing out liquid.
We fabricated two different kinds of composite materials for absorbing microwave in a frequency range of 2 to 18 GHz using coaxial airline and thru-reflect-line (TRL) method. The composite materials having carbon nanotube (CNT) with carbonyl iron (CI) or iron oxide (Fe3O4) were fabricated by mixing each components. Magnetic properties were measured by SQUID equipment. Complex permittivity and complex permeability were also obtained by measuring S-parameters of the toroidal specimen dispersing CI/CNT and Fe3O4/CNT into the 50 weight percent (wt%) epoxy resin. The real permittivity was improved by mixing the CNT however, the real permeability was same as pure magnetic powders. The CI/CNT had a maximum value of real permittivity and real permeability, 11 and 1.4 at 10 GHz, respectively. The CNT composites can be adapted to the radar absorbing materials, band width 8-12 GHz.
This paper presents the results of research on high performance concretes (HPC) modified by theaddition of polypropylene fibres (PP fibres). The scope of the research was the measurement of theresidual transport properties of heated and recooled concretes: gas permeability and surface waterabsorption. Seven types of concrete modified with fibrillated PP fibres were tested. Three lengths: 6,12 and 19 mm and three amounts of fibres: 0, 0.9 and 1.8 kg/m3 were used. The research programmewas designed to determine which length of fibres, used in which minimum amount, will, after thefibres melt, permit the development of a connected network and pathway for gases and liquids.
Chemical bonded resin sand mould system has high dimensional accuracy, surface finish and sand mould properties compared to green sand mould system. The mould cavity prepared under chemical bonded sand mould system must produce sufficient permeability and hardness to withstand sand drop while pouring molten metal through ladle. The demand for improved values of permeability and mould hardness depends on systematic study and analysis of influencing variables namely grain fineness number, setting time, percent of resin and hardener. Try-error experiment methods and analysis were considered impractical in actual foundry practice due to the associated cost. Experimental matrices of central composite design allow conducting minimum experiments that provide complete insight of the process. Statistical significance of influencing variables and their interaction were determined to control the process. Analysis of variance (ANOVA) test was conducted to validate the model statistically. Mathematical equation was derived separately for mould hardness and permeability, which are expressed as a non-linear function of input variables based on the collected experimental input-output data. The developed model prediction accuracy for practical usefulness was tested with 10 random experimental conditions. The decision variables for higher mould hardness and permeability were determined using desirability function approach. The prediction results were found to be consistent with experimental values.
The new investigation method of a permeability of ceramic moulds applied in the investment casting technology, is presented in the paper. Some concepts of performing permeability measurements are shown. Investigations in which the influence of the solid phase fraction in the liquid ceramic moulding sand (LCMS) on a permeability of a multi-layer ceramic mould were performed and discussed. The permeability was estimated during two the most important stages of the technological process: in the first – after wax melting and in the second – after mould annealing. Also an influence of the matrix grain sizes (material for sprinkling) on a ceramic mould permeability was estimated.
This study deals with the behavior of composite blends constituted of rigid and impervious grainsincluded in saturated clay paste of kaolin, considered as permeable and deformable. Permeabilitytests performed during standard oedometr tests (before each load step) highlight the key role ofthe original and actual state of the clay paste, and show the existence of a threshold of sandgrain concentration above which a structuring effect influences its permeability. In the light ofthese experiments some usual homogenization methods (with simplifying assumptions to make theproblem manageable) are considered in order to model the mixture permeability. Qualitative andquantitative comparisons with experimental data point out their respective domain of interest andlimitations of such approaches.
The objective of this investigation was comparing the penetration of chloride ions in ordinary and air-entrained concretes containing a waste material Fluidized Bed Combustion Fly Ash (FBCFA). All concretes were tested with 15% and 30% cement replacement by FBCFA, with the same water-binder ratio of 0.45. Two kinds of fly ash coming from fluid bed combustion in two power plants in Poland have been used. In this study the rapid chloride permeability test – Nordtest Method BUILD 492 method – was used. The microstructure of the concrete was analyzed on thin polished sections and the measurement of air voids sizes and their distribution, using digital image analysis, was carried on according to PN-EN 480-11:2008. Obtained results have shown a significant influence of partial cement replacement by FBCFA on the chloride ions movements in concrete. It has been found that this kind of addition reduced considerably the chloride ion penetration. The influence of air entrainment on the chloride diffusion coefficients was also measured and it was shown that application of air-entraining admixture for concretes with FBCFA reduce the chloride diffusion coefficient but it should be used with caution.