Simulation of a Refrigeration Compressor evaluating accuracy of results with variation in 3D component discretization

The current digital era has been providing great advantages for every task that relies on data processing. Engineering is not an exception, numerical simulation methods have been used more and more for product design. It is basically a predictive method, where the most relevant physical phenomena taking place inside the product are described by equations. They are numerically solved demanding a great amount of data processing especially for the simulation of large systems in transient regimes. One of the most challenging cases are those where the phenomena is highly dependent on spatial aspects, demanding a three dimensional (3D) approach to the analysis. The space or component is discretized into small volumes, or elements, and a set of equations have to be solved for each one of them. This might be challenging even for the latest generation computers concerning the processing time, because the amount of elements might be as much as millions. On the other hand, solutions modeling the geometry and associated physics as one dimensional (1D) volumes drastically reduce the processing time, but sometimes are less accurate. In this work we simulated a hermetic refrigeration compressor in a transient stable condition developing a hybrid solution, a 1D or 3D approach was applied to each separate component of the system according to its characteristics. Different levels of discretization were employed for the 3D parts and their effect on the results was evaluated. Among the results we could clearly see that some phenomena demand a certain level of discretization to be modeled, which was not possible with a pure 1D approach. However a very high level of discretization is sometimes not necessary as a lower level is able to properly describe the phenomena. Three components in a compressor were modeled with three different levels of discretization generating many possible configurations for the whole compressor; the results of some of them were compared with each other and with the experimental data showing good agreement

Modeling A Reciprocating Compressor Using A Two-Way Coupled Fluid And Solid Solver With Automatic Grid Generation And Adaptive Mesh Refinement

Computational fluid dynamics has been increasingly used in the design and analysis of reciprocating compressors over the last several years. One of the major challenges in the use of such tools is the creation of the numerical grid on which the modeled equations are solved. Since these compressors typically consist of many interconnected and moving parts, manual creation of the grid can be labor-intensive. Furthermore, it is necessary that the choice of grid yields a sufficiently resolved solution, so that the numerical error is significantly less than the modeling error. In this work, a small displacement refrigeration compressor is modeled using a numerical grid created with an automatic meshing approach. The grid is then automatically adapted to the flow based on the local flow field variables at each time step. This cut-cell based grid matches the supplied fluid volume exactly and permits general motion of all bounding surfaces. An explicit two-way coupled approach is used to account for the fluid-structure interaction between the deforming reed valves and the flow. The fluid is solved using a finite-volume approach, whereas the solid is solved using a finite-element model. The model is validated in comparison to measured mass flow rate, pressure, temperature, and valve lift for two different operation conditions and two different working fluids, namely R-404a and R-449a. The numerical accuracy of the calculations is demonstrated through an automated grid convergence study, and the effect of the grid and time-step resolution on the pressure pulsations and valve lift is shown. While computations on a relatively coarse grid yield power, mass flow rate, and pressure oscillation frequency comparable to measurements, a finer mesh is required inside the cylinder and in the discharge muffler to predict adequately the amplitude of the pressure fluctuations

Molecular and morphological markers for rapid distinction between 2 Colletotrichum species

Endophytic microorganisms reside asymptomatically within plants and are a source of new bioactive products for use in medicine, agriculture, and industry. Colletotrichum (teleomorph Glomerella) is a fungus widely cited in the literature as a producer of antimicrobial substances. Identification at the species level, however, has been a problem in this type of study. Several authors have reported the presence of endophytic fungi from the medicinal plant Maytenus ilicifolia (espinheira-santa) in Brazil that has antimicrobial activity against various pathogens. Therefore, Colletotrichum strains were isolated from M. ilicifolia and identified based on morphology, RAPD markers, sequence data of the internal transcribed spacer regions (ITS-1 and ITS-2), the 5.8S gene, and species-specific PCR. The analyses suggested the presence of 2 species, Colletotrichum gloeosporioides and Colletotrichum boninense. Two morphological markers were characterized to allow C. gloeosporioides and C. boninense to be distinguished quickly and accurately. The molecular diagnosis of C. boninense was confirmed by using Coll and ITS4 primers. This species of Colletotrichum is reported for the first time in M. ilicifolia.Universidade Estadual de Ponta Grossa (UEPG)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Neotropical freshwater fisheries : A dataset of occurrence and abundance of freshwater fishes in the Neotropics

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications