THE PURPOSE. Improving the energy efficiency of open cell foam materials with different geometries (SC, BCC, FCC, DEM) and with different medium porosities (ε=0.7; ε=0.75; ε=0.8; ε=0.85; ε=0.9; ε=0.95) by numerical simulation. To determine the influence of the geometry and porosity of an open cell foam material on the values of pressure drop, heat flux and energy efficiency factor.METHODS .Numerical simulation was carried out using the ANSYS Fluent 19.2 software package. Geometric models of porous structures are sets of intersecting spheres with different packing structures: periodic Simple Cubic packing (SC), Face Centered Cubic packing (FCC), Body Centered Cubic packing (BCC), and random structure generated by the discrete element method (DEM).The calculations were carried out at the following air flow velocities: 0.01; 0.05; 0.25; 0.5; 0.75; 1; 1.25 m/s.RESULTS. Atair flow velocities of 0.01 m/s and 0.05 m/s, all the studied structures show approximately the same heat flux. With porosity values ε=0.75; ε=0.8; ε=0.85 the highest values of heat flow were shown by the FCC structure, with porosity ε=0.7; ε=0.9; ε=0.95 the BCC structure had the highest heat flux. This is explained by the fact that, at the corresponding porosity values, the FCC or BCC structure had the largest surface area, which provided the largest heat flux. With the porosities of media ε=0.7 and ε=0.75, the BCC and FCC cell packages show a high pressure drop. With the porosities of media ε=0.8 and ε=0.85, the highest pressure drop corresponds to FCC cell packing, and for porosities ε=0.9 and ε=0.95, to BCC cell packing.CONCLUSION. With equal high porosity, the BCC cell packing provides a higher value of heat flux than the FCC structure. The SC package has the lowest heat flux values for all studied porosities. The SC package also has the lowest pressure drop values and therefore the highest energy efficiency values.
The stable and uninterrupted work of the energy sector enterprises largely determines the economic development of the country. At the same time, the reliability of energy systems and complexes depends on the technical condition of the energy transportation equipment. In this regard, there is an urgent need to monitor the technical condition of the equipment. Currently, there are various types of non-destructive testing used for diagnostics, but none of them is universal, and many of them only allow to find defects of a certain type. In this connection, there is a topical issue of improving the methods for assessing the technical condition of equipment during the transportation of energy carriers in energy systems and complexes. This paper presents an information and diagnostic complex that implements the proposed technical solution and tests the methodology.
THE PURPOSE. To consider the problems that arise when creating a composite heatinsulating material, including a layer of microspherical granules. Numerical modeling of a composite material with different volume content of microspheres and different options for the formation of voids. Determination of the influence of the presence of zones not occupied by microgranules on the insulating properties of the composite material. Determination of the influence of the volume content of microspherical granules on the heat flux through the composite material.METHODS. Numerical simulation was carried out by creating models of elementary cubic cells of a composite with a package of 27 microspheres in the ANSYS Fluent 19.2 software package. The evaluation of the insulating properties was carried out by measuring the thermal conductivity coefficient.RESULTS. The article investigates the influence of the presence of zones not occupied by microspherical granules on the thermal insulation properties of a composite material. Models of elementary cubic cells with different volume content of microgranules are constructed. Models of elementary cells are built with various options for the formation of voids, such as the removal of a vertical or horizontal row of granules and the compaction of granules vertically or horizontally.CONCLUSION. The removal of microgranules has a significant effect on the insulating properties of the composite. The lowest thermal conductivity coefficient was obtained for a simple cubic cell with a volume content of microgranules φ = 40%. The presence of voids in the material contributes to large heat losses, and in the case of a vertical through channel, the heat losses are greater than for a horizontal through channel. In the case of densification of spheres, heat losses in the zone not occupied by microgranules are compensated by a decrease in the heat flux in the area with densification of spheres.
THE PURPOSE. To consider the problems of reliability of pipeline systems of housing and communal services. To analyze existing methods for assessing the technical condition of pipelines. To develop an improved technique that allows you to search for various types of defects in pipelines. To develop a device for inertial excitation of low-frequency diagnostic vibration vibrations. To develop software in the LabVIEW environment for collecting, storing and processing signals from a sensitive sensor (piezoelectric sensor) installed on a pipeline. To conduct a series of experimental studies to te st the proposed methodology. METHODS. The method of inertial excitation of vibrations was used to excite vibrations in the wall of the investigated pipeline. To search for the natural frequencies of vibrations of the pipeline under study, mathematical mode ling methods were used, implemented in the ANSYS software package. During the experiments, the fast Fourier transform method was used to process the signals coming from the piezoelectric sensor. RESULTS. The article presents a technique for assessing the t echnical condition of pipelines, as well as a device for inertial excitation of vibrations. The article presents the results of experimental studies on a fiberglass pipeline, the results showed that when an oscillatory wave passes through the wall of a defect-free pipeline, its amplitude changes insignificantly. If there is a defect in the wall of the investigated pipeline, the vibration amplitude will be much weaker due to the dissipation of vibrational energy in the place of the defect. Thereby, it is pos sible to determine not only the presence of a defect, but also its size by the degree of attenuation of the signal amplitude CONCLUSION. The proposed technique is the basis for the creation of a new measuring and diagnostic complex for vibration control of pipelines.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.