Defect and Diffusion Forum Vol. 353

Abstract: The paper deals with modeling and simulation of methane flow through the porous environment using the CFD (Computational Fluid Dynamics) software Fluent. We compare three situations, which can occur in areas, where mining activities were closed few years ago, in this article. First case is modeling of methane flow through the rocks. Second event is situation where the thin water layer is situated at the surface. The last one is occurrence of groundwater. The article responds to the need for knowledge of natural processes in the given area and it follows our previous papers [1], [2]. Software Gambit was used for creating a geometric model of the working area, for modeling the flow of gas it was used CFD software, Fluent from ANSYS, Inc..

Abstract: Measuring of thermal distribution in certain material was done in Matlab. Obtained data are processed and displayed in fully 3D environment (virtual reality) using X3D. Paper deals with data processing and conversion from Matlab into X3D. Further development of visualization is discussed too – visualization of thermal gradient, Integration of measured a visualized data into real object or technological process visualization. The aim of this topic is to present information about discontinuities in solid materials.

Abstract: Three types of eutectic carbides, M₂C, M₆C and MC, were revealed in the as cast microstructure of the AISI M2 type high-speed steel inoculated with different additions to the melt. The thermal stability of these carbides were analysed in the range of austenitising temperature from 1180°C up to 1260°C. It was found that the M₆C and MC eutectic carbides were stable up to 1240°C and 1260°C, respectively. The M₂C carbide started to decompose at substantially lower austenitising temperature and its thermal stability was shown to depend on both the morphology and the chemical composition, and the origin of the inoculating additions used before casting.

Abstract: RTM process is widely used for the production of high quality fiber reinforced composites parts. Computer simulations can play an important role in optimization of RTM processes by reducing risks and costs. In this paper, we present a two dimensional mathematical modelling for the mold filling stage in RTM process. It was used a two phase model (air-resin) which neglects the capillary and gravitational effects and considers all phases incompressible. The set of partial differential equations, expressed in boundary-fitted coordinates, are discretized by using the finite volume method and solved using a fully implicit methodology and the Newton's method. To validate the methodology, numerical and experimental data of the filling time and flow front position along the process are compared and good agreement was obtained.

Abstract: Paddle dryer, one kind of indirect dryers, is widely used in removing moisture content of many materials, such as brown coal, sewage sludge, and biomass. For many applications, the materials to be dried are low-valued or even wastes, so the drying energy consumption becomes the critical issue. One way to reduce the energy consumption is to introduce solar-drying technology. In this paper, firstly, we present a paddle dryer system configuration with concentrated solar energy (CSE) device, which consists of trough-type collectors, thermal storage tanks and auxiliary parts. Then a calculating model is developed to design the drying system. Examples with typical solar radiation conditions in Nanjing, China are illustrated. The energy-saving rate (η), i.e. the ratio of the provided solar energy to the total energy required by the drying process on one-day basis, is evaluated. The developed lab prototype is finally described in brief.

Abstract: Studies were conducted on method of processing and chemical compositions of date pit for possible applications in enhanced oil recovery. Date seed from the eastern province of Saudi Arabia were washed by sonication and sun dried. The dried seeds were ground, de-oiled and made into solutions using alkaline. Physicochemical properties and chemical compositions of the de-oiled date seed powder were investigated using SEM and FTIR. The properties of the powder solutions were investigated by evaluating their viscosifying properties. Results of elemental analysis showed that the powder contains 57.41 - 65.84% carbon and 34.16 - 41.35% oxygen. The peak values in the range 3369.6 - 3417.3cm^-1 obtained from FTIR are indicative of the presence of OH functional groups. The results obtained from viscosity measurement revealed that date seed be utilized as viscosity modifier to alter the mobility ratio in enhanced oil recovery processes. In addition, the multiple hydroxyl functional groups contained in date pit powder can be made available for organic reactions to produce surfactants and polymeric polyols that can be used for wettability and interfacial tension (IFT) alteration as employed in enhanced oil recovery operations. Furthermore, more studies need to be done to investigate and improve other relevant properties of the powder solution so that it can be used in near reservoir conditions. Accordingly, future work will be focused on detailed investigation on the use of the powder to alter mobility ratio, wettability and IFT.

Abstract: Studies in polymer composites reinforced with vegetable fiber show that they are enough sensitive to influences from environmental agents such as water and temperature. The moisture causes degradation of the mechanical properties of natural fiber reinforced composites to a large extent when compared to synthetic fiber reinforced composites. This is a consequence of the higher moisture absorption, and the hydrofilic nature of the natural fiber. In this sense, the purpose of this work is to study theoretically the water absorption in unsaturated polyester composites reinforced with caroá natural fiber (Neoglaziovia variegata) at the temperature 50°C. The composite had a weight composition of 30% caroá and 70% unsaturated polyester resin and dimensions of 20× 20× 3 mm³. Results of the average moisture content and moisture content distribution during the absorption process are presented and analyzed. Comparison between numerical and experimental data of the average moisture content presented good agreement. We conclude that the water absorption rate is faster in the vertex region of the composites.

Abstract: This study analyzed nine polypropylene (PP) and low-density polyethylene (LDPE) blends where the mass concentrations of each sample were changed, proportionally. The aim was to investigate the tensile strength by means of these polymers best combination, before and after its exposal to gamma rays. The results showed that the 20/80 - PP/LDPE blend had a better performance concerning mechanical properties after irradiation, where the maximums tensile stress had an average increase of 30% in 30 and 50 kGy doses and 33% in the 200 kGy dose. On the other hand, it was verified that the higher blend's PP concentration, the higher its tensile strength will be (except for 100 kGy and 200 kGy doses which PP concentration over 70% can cause eventual degradation in the polymeric chains of the blend).

Abstract: Rice husk ash (RHA) is the product of rice husk pyrolysis or combustion, which contains inherent ash in original rice husk and non-converted fixed carbon. Due to large amounts of inherent silicon dioxide in rice husk, the decarbonized residue of RHA has great value as industrial materials. One basic method to remove carbon from RHA is roasting. Because of low carbon content in RHA and low roasting reaction velocity, the roasting process takes a long time. In this case, fixed-bed roasting is suitable for removing carbon from RHA. In the present work, experimental study on RHA decarbonization is conducted based on a specially-designed multi-section fixed-bed roasting. The experimental results show that under the experimental conditions, the flame propagation spread of RHA in fixed beds is in the range 0.833 to 0.121mm/s. The results documented in this paper provide the basis for further developing large-scale engineering devices.

Abstract: Polystyrene particles of 4 μm in diameter are aggregated as the monolayer clusters rearranged themselves when the compressive forces are applied to the clusters. Oriented structures of the clusters are then examined and characterized the failure mechanisms of two-dimensional (2D) aggregation. Failure mechanisms cause rearrangement of particles within the aggregates. Their flaw locations of each applying force change due to the particle bonding-rebonding themselves. Particles can move either relatively to each other or the small aggregates. Even though, these orientations occur in the small scale and barely significant, disturbed particles gradually accumulate stress. Small aggregates or particles inside the bulk perhaps cannot immediately change the cluster shape, but regularly oriented until reaching to yield. Compression to 2D aggregates can make an existing dislocation and fractures of this aggregated structure. Crack propagation of the dense is possible to proceed dynamically. The clusters collapse until reaching to yield. Two-dimensional structures of compressive aggregated polystyrene are always mechanical instable that increases in propagating rupture. Therefore, the quake will reasonably occur.