Reduced model for the thermo-fluid dynamic analysis of a power transformer radiator working in ONAF mode

This work introduces an extension of the semi-analytical reduced model presented in G. Ríos Rodriguez et.al., App Thermal Eng, 112:1271–1280 (2016); with the aim of analyzing the thermo-fluid dynamic behavior of a power transformer radiator working in ONAF (Oil Natural Air Forced) mode, considering vertical blowing of the fans. The objective of this research paper is the development of a numerical tool to be used during the design process of power transformers in order to obtain more detailed information about the radiators performance, either they are working in ONAF or ONAN (Oil Natural Air Natural) mode. Since it is observed both in the experimental measurements and in the numerical simulations that not all the radiator panels are blown by a single fan, the reduced model here presented considers a mixed situation wherein the heat is removed by natural convection in a fraction of the radiator while in the rest the heat is removed by forced convection. As a consequence, besides adding to the set of conservation equations introduced in G. Ríos Rodriguez et.al., App Thermal Eng, 112:1271– 1280 (2016); those corresponding to the momentum and energy balance for considering forced heat convection transfer, there appears the need of introducing additional equations for coupling the natural and forced heat convection transfer models. The reduced model developed in this work is applied to estimate different characteristic parameters of a power transformer radiator working in ONAF mode, like the oil flow rate, dissipated power, outlet and inlet oil temperatures, among others. The computed results are compared to those obtained by CFD simulations and experimental measurements carried out on an ad-hoc workbench for validation purposes. It is found that the reduced model reproduces with acceptable accuracy the values of the most important design variables at a very low computation cost. In this manner, it can be considered as a reliable and valuable tool in the design of power transformers, allowing to carry out parametric studies.Publicado en: Mecánica Computacional vol. XXXV, no. 4Facultad de Ingenierí

Reduced model for the thermo-fluid dynamic analysis of a power transformer radiator working in ONAF mode

This work introduces an extension of the semi-analytical reduced model presented in G. Ríos Rodriguez et.al., App Thermal Eng, 112:1271–1280 (2016); with the aim of analyzing the thermo-fluid dynamic behavior of a power transformer radiator working in ONAF (Oil Natural Air Forced) mode, considering vertical blowing of the fans. The objective of this research paper is the development of a numerical tool to be used during the design process of power transformers in order to obtain more detailed information about the radiators performance, either they are working in ONAF or ONAN (Oil Natural Air Natural) mode. Since it is observed both in the experimental measurements and in the numerical simulations that not all the radiator panels are blown by a single fan, the reduced model here presented considers a mixed situation wherein the heat is removed by natural convection in a fraction of the radiator while in the rest the heat is removed by forced convection. As a consequence, besides adding to the set of conservation equations introduced in G. Ríos Rodriguez et.al., App Thermal Eng, 112:1271– 1280 (2016); those corresponding to the momentum and energy balance for considering forced heat convection transfer, there appears the need of introducing additional equations for coupling the natural and forced heat convection transfer models. The reduced model developed in this work is applied to estimate different characteristic parameters of a power transformer radiator working in ONAF mode, like the oil flow rate, dissipated power, outlet and inlet oil temperatures, among others. The computed results are compared to those obtained by CFD simulations and experimental measurements carried out on an ad-hoc workbench for validation purposes. It is found that the reduced model reproduces with acceptable accuracy the values of the most important design variables at a very low computation cost. In this manner, it can be considered as a reliable and valuable tool in the design of power transformers, allowing to carry out parametric studies.Publicado en: Mecánica Computacional vol. XXXV, no. 4Facultad de Ingenierí

Cadera flotante: análisis comparativo de resultados y lesiones asociadas

Objetivo: Describir los tiempos de internación, cirugía y rehabilitación de una serie de pacientes con cadera flotante. El objetivo secundario fue comparar los resultados obtenidos en función de la reinserción laboral con los de pacientes que sufrieron fracturas de pelvis o acetábulo sin fractura femoral asociada. Materiales y Métodos: Estudio descriptivo, retrospectivo y multicéntrico de pacientes con trauma de pelvis y acetábulo de alta energía, divididos en dos grupos de estudio según la presencia de fractura de fémur asociada homolateral (cadera flotante) para su comparación, durante el período comprendido entre enero de 2014 y marzo de 2019. Resultados: Se incluyó a 102 pacientes con trauma de pelvis o acetábulo agrupados en 2 poblaciones según la presencia de cadera flotante (cadera flotante 23; pelvis/acetábulo 79). Las medianas de días de internación [cadera flotante 15,5 (rango 4-193); pelvis/acetábulo 7 (rango 3-31); p = 0,0001] y de la cantidad de cirugías por paciente [cadera flotante 5 (rango 3-8); pelvis/acetábulo 2 (rango 1-4); p = 0,0001] fueron mayores en los pacientes con cadera flotante. Además, la incapacidad laboral temporaria fue más alta (p = 0,00012), sin diferencias significativas en la tasa de recalificación laboral (p = 0,11). Conclusión: La asociación de la lesión cadera flotante aumentó significativamente el tiempo de internación, los procedimientos quirúrgicos necesarios y el tiempo de recuperación según la incapacidad laboral temporaria en pacientes con trauma de pelvis o acetábulo

Thermal analysis of 8.5 MVA disk-type power transformer cooled by biodegradable ester oil working in ONAN mode by using advanced EMAG–CFD–CFD coupling

Power transformers are the first devices used to transfer the electrical energy produced in power plants to the grid to supply the industrial and individual receivers with electricity. The heat generation in windings and core, being an effect of the power losses, is usually dissipated in large units by using mineral oils, which are harmful to the environment. Nowadays, the industry and global society seek environmentally-friendly alternatives. One of the most promising substitute for their high biodegradability, safety in operation, and favourable thermo-physical properties are natural ester oils. For this reason, a numerical study of 8.5 MVA disk-type power transformer cooled using conventional mineral oil and a commercially used rapeseed ester oil is presented in this paper. Moreover, due to different thermal behaviour of the considered oils, the comparison was made for the unit working in different seasons of hot and moderate climate zones (Argentina and Poland). In the numerical approach, electromagnetic (EMAG) and computational fluid dynamics (CFD) models were used for a detailed study of the selected device. In particular, a novel and very efficient EMAG–CFD–CFD coupling procedure was developed to assess the cooling of the large power transformer. Such a coupled computational procedure allowed for the detailed investigation of the power loss, oil flow characteristics, and temperatures with a satisfying computational effort. The results showed that the average windings temperatures are higher by 2–9 K when the ester oil is used, dependent on the ambient conditions. The hotspot temperature in the low voltage windings increased by up to 9 K and up to 18 K in the high voltage windings using ester oil. According to the results, the oil duct construction requires modification in the high voltage region for transformers cooled using mineral oil in cold climate conditions.Fil: Stebel, Michal. Silesian University Of Technology; PoloniaFil: Kubiczek, Krzysztof. Silesian University Of Technology; PoloniaFil: Rios Rodriguez, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Palacz, Michal. Silesian University Of Technology; PoloniaFil: Garelli, Luciano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Melka, Bartlomiej. Silesian University Of Technology; PoloniaFil: Haida, Michal. Silesian University Of Technology; PoloniaFil: Bodys, Jakub. Silesian University Of Technology; PoloniaFil: Nowak, Andrzej J.. Silesian University Of Technology; PoloniaFil: Lasek, Pawel. Silesian University Of Technology; PoloniaFil: Stepien, Mariusz. Silesian University Of Technology; PoloniaFil: Pessolani, Francisco. Tadeo Czerweny S.a.; ArgentinaFil: Amadei, Mauro. Tadeo Czerweny S.a.; ArgentinaFil: Granata, Daniel. Tadeo Czerweny S.a.; ArgentinaFil: Storti, Mario Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Smolka, Jacek. Silesian University Of Technology; Poloni

Essential dynamics for the study of microstructures in liquids

Essential Dynamics (ED) is a powerful tool for analyzing molecular dynamics (MD) simulations and it is widely adopted for conformational analysis of large molecular systems such as, for example, proteins and nucleic acids. In this study, we extend the use of ED to the study of clusters of arbitrary size constituted by weakly interacting particles, for example, atomic clusters and supramolecular systems. The key feature of the method we present is the identification of the relevant atomic-molecular clusters to be analyzed by ED for extracting the information of interest. The application of this computational approach allows a straightforward and unbiased conformational study of the local microstructures in liquids, as emerged from semiclassical MD simulations. The good performance of the method is demonstrated by calculating typical observables of liquid water, that is, NMR, NEXAFS O1s, and IR spectra, known to be rather sensitive both to the presence and to the conformational features of hydrogen-bonded clusters. \ufffd 2014 Wiley Periodicals, Inc

The conformation of constitutive DNA interaction sites for eukaryotic DNA topoisomerase I on intrinsically curved DNAs.

The analysis of the sites which are cleaved constitutively and preferentially by eukaryotic DNA topoisomerase I on two intrinsically curved DNAs reveals the conformational features that provoke the cleavage reaction on the curve-inducing sequence elements in the absence of supercoiling. This analysis is based on the observation (Caserta et al. (1989) Nucleic Acids Res. 17, 8521-8532 and (1990) Biochemistry 29, 8152-8157) that the reaction of eukaryotic DNA topoisomerase I occurs on two types of DNA sites: sites S (Supercoiled induced) and sites C (Constitutive, whose presence is topology-independent). We report that sites C are abundant on the intrinsically curved DNAs analyzed. The DNAs studied were two intrinsically curved segments of different origin: the Crithidia fasciculata kinetoplast DNA and the bent-containing domain B of the Saccharomyces cerevisiae ARS1. On these DNA segments DNA topoisomerase I cleaves at the junctions between the poly(A) tracts and mixed-sequence DNA. Analysis of the conformation of the double helix around the cleavage sites has revealed that the reaction occurs in correspondence of a defined DNA conformational motif. This motif is described by the set of Eulerian angular values that define the axial path of DNA (helical twist, deflection angle, direction) and of the orthogonal components of wedge (roll and tilt)

In vitro preferential topoisomerization of bent DNA.

The steps of the topoisomerization reaction by calf thymus DNA topoisomerase I on a DNA domain containing an intrinsically bent DNA sequence have been analyzed. High preferentiality of binding, cleavage and topoisomerization on the bent segment relative to the rest of the DNA domain was observed. These studies show the importance of the local DNA conformation in the reaction of eukaryotic DNA topoisomerase I and the interest of the use of this enzyme as a tool for the analysis of DNA conformation and DNA dynamics