http://hdl.handle.net/2117/218 Sat, 18 May 2013 15:47:59 GMT 2013-05-18T15:47:59Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/16259 Title: Rehabilitación energética de edificios escolares en clima mediterráneo: caso de estudio, Barcelona Authors: Bosch González, Montserrat; Rodríguez Cantalapiedra, Inma; Álvarez del Castillo, Javier Abstract: necesidad de reducir el consumo energético se hace cada día más evidente, especialmente en Europa debido a su situación de dependencia energética de países externos a la Unión y también por razones relacionadas con el impacto ambiental y las emisiones asociadas. En este contexto, la rehabilitación energética de edificios es una línea de trabajo prioritaria que actúa sobre el parque edificado, y los edificios públicos deben ser un modelo o ejemplo para impulsar este tipo de actuaciones. Los centros docentes, con un potencial de ahorro muy importante y con unos consumos energéticos asociados básicamente a dos grandes conceptos, la iluminación y la climatización, pueden considerarse como un laboratorio de investigación en cuanto a eficiencia energética. A partir de las experiencias adquiridas durante más de 10 años se ha desarrollado una metodología de análisis para la intervención en edificios docentes en Barcelona con los siguientes objetivos: definir los indicadores estratégicos para identificar las oportunidades de ahorro, evaluar las posibles medidas de reducción de consumos a partir de la limitación de la demanda, analizar y dar contenido al papel de cada uno de los actores que intervienen en las estrategias de uso y gestión de los edificios escolares y establecer los criterios que deben considerarse para realizar las futuras intervenciones de rehabilitación energética. El método, como manera de pensar ordenadamente, ha de permitir optimizar los recursos y descubrir les rutas de trabajo que nos conduzcan al objetivo final: reducir el consumo energético del parque edificado http://hdl.handle.net/2117/16259 Bosch González, Montserrat; Rodríguez Cantalapiedra, Inma; Álvarez del Castillo, Javier no necesidad de reducir el consumo energético se hace cada día más evidente, especialmente en Europa debido a su situación de dependencia energética de países externos a la Unión y también por razones relacionadas con el impacto ambiental y las emisiones asociadas. En este contexto, la rehabilitación energética de edificios es una línea de trabajo prioritaria que actúa sobre el parque edificado, y los edificios públicos deben ser un modelo o ejemplo para impulsar este tipo de actuaciones. Los centros docentes, con un potencial de ahorro muy importante y con unos consumos energéticos asociados básicamente a dos grandes conceptos, la iluminación y la climatización, pueden considerarse como un laboratorio de investigación en cuanto a eficiencia energética. A partir de las experiencias adquiridas durante más de 10 años se ha desarrollado una metodología de análisis para la intervención en edificios docentes en Barcelona con los siguientes objetivos: definir los indicadores estratégicos para identificar las oportunidades de ahorro, evaluar las posibles medidas de reducción de consumos a partir de la limitación de la demanda, analizar y dar contenido al papel de cada uno de los actores que intervienen en las estrategias de uso y gestión de los edificios escolares y establecer los criterios que deben considerarse para realizar las futuras intervenciones de rehabilitación energética. El método, como manera de pensar ordenadamente, ha de permitir optimizar los recursos y descubrir les rutas de trabajo que nos conduzcan al objetivo final: reducir el consumo energético del parque edificado http://hdl.handle.net/2117/19161 Title: Estudio comparativo del conformado en caliente de un acero microaleado usando criterios termodinámicos continuos y criterios fenomenológicos Authors: Alcelay Larrión, José Ignacio; Al Omar Mesnaoui, Anas; Prado Pozuelo, José Manuel Abstract: En las últimas décadas, los mapas de procesado han sido ampliamente utilizados para diseñar, controlar y optimizar los procesos de conformado en caliente. En el presente trabajo, se presenta un estudio comparativo entre mapas de procesado elaborados usando criterios termodinámicos continuos y criterios fenomenológicos. Por ello, se llevaron a cabo ensayos de compresión en caliente en el rango de temperaturas 900 - 1150 ºC y de velocidades de deformación i: = 10-4 - 10 s-1 . El comportamiento en caliente del acero estudiado ha sido estudiado analizando las curvas de fluencia y la interacción entre el comportamiento microestructural y los parámetros de control del proceso de deformación. El estudio comparativo de los mapas de procesado muestra la diferencia entre las posiciones de los distintos dominios de deformación plástica, según el criterio de inestabilidad usado. Además, el análisis de dichos mapas indica que el acero estudiado no sufre ningún tipo de inestabilidad plástica . Sin embargo, los mapas correspondientes a la deformación ¡; = 0,6 revelan la existencia de un dominio de recristalización dinámica, considerado como el dominio más eficiente dentro de la región segura de procesado. Este dominio está centrado a 1150 ºC y 10 s·1.; In the last decades, processing maps have been widely used to design, control and optimize hot forming processes. In this paper, we present a comparative study of processing maps constructed using phenomenological and thermodynamic continuum criteria. Therefore, hot compression tests were carried out in the temperature and strain rate ranging from 900 to 1150 ºC and 10-• to 10 s-1. The hot deformation behavior of studied steel has been investigated analyzing the flow curves and the interaction between the microstructural behavior and parameters control of the deformation process. The comparative study of processing maps show the difference between the positions of plastic deformation domains predicted by the two instability criteria. The analysis of the maps indicates that the steel does not undergo any plastic instability. However, the maps corresponding to deformation E = 0,6 reveal the existence of a domain of dynamic recrystallization, considered the most efficient domain within the safe region processing. This domain is centered at 1150 ºC and 10 s-1. Fri, 10 May 2013 13:22:35 GMT http://hdl.handle.net/2117/19161 2013-05-10T13:22:35Z Alcelay Larrión, José Ignacio; Al Omar Mesnaoui, Anas; Prado Pozuelo, José Manuel no En las últimas décadas, los mapas de procesado han sido ampliamente utilizados para diseñar, controlar y optimizar los procesos de conformado en caliente. En el presente trabajo, se presenta un estudio comparativo entre mapas de procesado elaborados usando criterios termodinámicos continuos y criterios fenomenológicos. Por ello, se llevaron a cabo ensayos de compresión en caliente en el rango de temperaturas 900 - 1150 ºC y de velocidades de deformación i: = 10-4 - 10 s-1 . El comportamiento en caliente del acero estudiado ha sido estudiado analizando las curvas de fluencia y la interacción entre el comportamiento microestructural y los parámetros de control del proceso de deformación. El estudio comparativo de los mapas de procesado muestra la diferencia entre las posiciones de los distintos dominios de deformación plástica, según el criterio de inestabilidad usado. Además, el análisis de dichos mapas indica que el acero estudiado no sufre ningún tipo de inestabilidad plástica . Sin embargo, los mapas correspondientes a la deformación ¡; = 0,6 revelan la existencia de un dominio de recristalización dinámica, considerado como el dominio más eficiente dentro de la región segura de procesado. Este dominio está centrado a 1150 ºC y 10 s·1. http://hdl.handle.net/2117/19150 Title: Small-scale characteristics and turbulent statistics of the flow in an external gear pump by time-resolved PIV Authors: Ertürk, S.; Vernet, Anton; Pallarés, J.; Castilla López, Roberto; Raush Alviach, Gustavo Adolfo Thu, 09 May 2013 12:44:56 GMT http://hdl.handle.net/2117/19150 2013-05-09T12:44:56Z Ertürk, S.; Vernet, Anton; Pallarés, J.; Castilla López, Roberto; Raush Alviach, Gustavo Adolfo no PIV, Spatial resolution, Turbulent flow, External gear pump, Dissipation rate http://hdl.handle.net/2117/19113 Title: Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications : in vitro study Authors: Vlad, María Daniela; Valle Mendoza, Luis Javier del; Poeata, I.; López López, José; Torres Cámara, Ricardo; Barraco Serra, Marc; Fernández Aguado, Enrique Abstract: In this study, the cytocompatibility of new ‘iron-modified/alpha-tricalcium phosphate (IM/α-TCP) and calcium sulfate dihydrate (CSD)’ bone cement (IM/α-TCP/CSD-BC) intended for spinal applications has been approached. The objective was to investigate by direct-contact osteoblast-like cell cultures (from 1 to 14 days) the in vitro cell adhesion, proliferation, morphology and cytoskeleton organization of MG-63 cells seeded onto the new cements. The results were as follows: (a) quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion, proliferation and viability were not affected with time by the presence of iron in the cements; (b) double immunofluorescent labeling of F-actin and α-tubulin showed a dynamic interaction between the cell and its porous substrates sustaining the locomotion phenomenon on the cements’ surface, which favored the colonization, and confirming the biocompatibility of the experimental cements; (c) SEM-cell morphology and cytoskeleton observations also evidenced that MG-63 cells were able to adhere, to spread and to attain normal morphology on the new IM/α-TCP/CSD-BC which offered favorable substratum properties for osteoblast-like cells proliferation and differentiation in vitro. The results showed that these new iron-modified cement-like biomaterials have cytocompatible features of interest not only as possible spinal cancellous bone replacement biomaterial but also as bone tissue engineering scaffolds. Description: Premi del "National University Research Council" del Ministeri d'Educació i Recerca de Romania, a autors romanesos per l'impacte de la seva recerca. Tue, 07 May 2013 09:56:44 GMT http://hdl.handle.net/2117/19113 2013-05-07T09:56:44Z Vlad, María Daniela; Valle Mendoza, Luis Javier del; Poeata, I.; López López, José; Torres Cámara, Ricardo; Barraco Serra, Marc; Fernández Aguado, Enrique no In this study, the cytocompatibility of new ‘iron-modified/alpha-tricalcium phosphate (IM/α-TCP) and calcium sulfate dihydrate (CSD)’ bone cement (IM/α-TCP/CSD-BC) intended for spinal applications has been approached. The objective was to investigate by direct-contact osteoblast-like cell cultures (from 1 to 14 days) the in vitro cell adhesion, proliferation, morphology and cytoskeleton organization of MG-63 cells seeded onto the new cements. The results were as follows: (a) quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion, proliferation and viability were not affected with time by the presence of iron in the cements; (b) double immunofluorescent labeling of F-actin and α-tubulin showed a dynamic interaction between the cell and its porous substrates sustaining the locomotion phenomenon on the cements’ surface, which favored the colonization, and confirming the biocompatibility of the experimental cements; (c) SEM-cell morphology and cytoskeleton observations also evidenced that MG-63 cells were able to adhere, to spread and to attain normal morphology on the new IM/α-TCP/CSD-BC which offered favorable substratum properties for osteoblast-like cells proliferation and differentiation in vitro. The results showed that these new iron-modified cement-like biomaterials have cytocompatible features of interest not only as possible spinal cancellous bone replacement biomaterial but also as bone tissue engineering scaffolds. http://hdl.handle.net/2117/19112 Title: Osteogenic biphasic calcium sulphate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications : in vivo study Authors: Vlad, María Daniela; Sindilar, E.V.; Mariñoso, Maria Lluïsa; Poeata, I.; Torres Cámara, Ricardo; López López, José; Barraco Serra, Marc; Fernández Aguado, Enrique Abstract: In this study, the biocompatibility and the osteogenic features of a new iron-modified α-tricalcium phosphate (IM/α-TCP) and calcium sulphate dihydrate (CSD) biphasic cement (IM/α-TCP/CSD-BC) have been investigated in terms of the in vivo cement resorption, bone tissue formation and host tissue response on sheep animal model. Histological evaluation performed on undecalcified cement–bone specimens assessed the in vivo behaviour. It has been shown that the new IM/α-TCP/CSD-BC has the ability to produce firm bone binding in vivo (i.e. bioactivity). Qualitative histology proved cement biocompatibility, osteoconduction and favourable resorption, mainly through a macrophage-mediated mechanism. The results showed that the new cements have biocompatible and osteogenic features of interest as possible cancellous bone replacement biomaterial for minimally invasive spinal surgery applications. Description: Premi del "National University Research Council" del Ministeri d'Educació i Recerca de Romania, a autors romanesos per l'impacte de la seva recerca. Tue, 07 May 2013 09:39:32 GMT http://hdl.handle.net/2117/19112 2013-05-07T09:39:32Z Vlad, María Daniela; Sindilar, E.V.; Mariñoso, Maria Lluïsa; Poeata, I.; Torres Cámara, Ricardo; López López, José; Barraco Serra, Marc; Fernández Aguado, Enrique no In this study, the biocompatibility and the osteogenic features of a new iron-modified α-tricalcium phosphate (IM/α-TCP) and calcium sulphate dihydrate (CSD) biphasic cement (IM/α-TCP/CSD-BC) have been investigated in terms of the in vivo cement resorption, bone tissue formation and host tissue response on sheep animal model. Histological evaluation performed on undecalcified cement–bone specimens assessed the in vivo behaviour. It has been shown that the new IM/α-TCP/CSD-BC has the ability to produce firm bone binding in vivo (i.e. bioactivity). Qualitative histology proved cement biocompatibility, osteoconduction and favourable resorption, mainly through a macrophage-mediated mechanism. The results showed that the new cements have biocompatible and osteogenic features of interest as possible cancellous bone replacement biomaterial for minimally invasive spinal surgery applications. http://hdl.handle.net/2117/18870 Title: Numerical simulation of wrap scroll temperature for refrigeration and air conditioning compressors Authors: Rovira Casals, Jordi; Rigola Serrano, Joaquim; Pérez Segarra, Carlos David; Oliva Llena, Asensio Abstract: Being part of a model which simulates the whole consecutive overall compression process in a scroll compressor by solving equations of mass, momentum and energy balance for fluid refrigerant (Rovira et al. ,2006), an updated version is presented. In this new model, an energy balance over the scroll wraps is implemented; where temperatures and heat fluxes are obtain ed dividing the wall into 36 parts (slices) each turn. The scroll wrap is divided into different solid slices; energy balance is carried out, taking into account: i) conduction along the scroll wrap; ii) convection heat transfer between each slice and each fluid chamber, with special attention on solid slice - fluid chamber contact at each time step. The numerical model shows the one dimensional and transient temperature, pressure and mass flow rate, at each fluid chamber along the scroll compressor, among detailed solid wrap temperature distribution. The whole numerical model has been experimentally validated against experimental data from technical literature (Halm,1997)(Chen et al.,2004a)(Chen et al.,2004b), comparing mass flow rate, discharge temperature, compression work and power consumption. Finally, the influence of wall temperatures and wall heat fluxes on the compressor performance and other output variables is analyzed. Thu, 18 Apr 2013 13:51:51 GMT http://hdl.handle.net/2117/18870 2013-04-18T13:51:51Z Rovira Casals, Jordi; Rigola Serrano, Joaquim; Pérez Segarra, Carlos David; Oliva Llena, Asensio no Being part of a model which simulates the whole consecutive overall compression process in a scroll compressor by solving equations of mass, momentum and energy balance for fluid refrigerant (Rovira et al. ,2006), an updated version is presented. In this new model, an energy balance over the scroll wraps is implemented; where temperatures and heat fluxes are obtain ed dividing the wall into 36 parts (slices) each turn. The scroll wrap is divided into different solid slices; energy balance is carried out, taking into account: i) conduction along the scroll wrap; ii) convection heat transfer between each slice and each fluid chamber, with special attention on solid slice - fluid chamber contact at each time step. The numerical model shows the one dimensional and transient temperature, pressure and mass flow rate, at each fluid chamber along the scroll compressor, among detailed solid wrap temperature distribution. The whole numerical model has been experimentally validated against experimental data from technical literature (Halm,1997)(Chen et al.,2004a)(Chen et al.,2004b), comparing mass flow rate, discharge temperature, compression work and power consumption. Finally, the influence of wall temperatures and wall heat fluxes on the compressor performance and other output variables is analyzed. http://hdl.handle.net/2117/18868 Title: Numerical simulation of the turbulent fluid flow through valves based on low mach models Authors: Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Ventosa, Jordi; Pérez Segarra, Carlos David; Oliva Llena, Asensio Abstract: The aim of the present paper is to carry out a group of numerical experiments over the fluid flow through the valve reed, using the CFD&HT code TermoFluids, an unstructure d and parallel object-oriented CFD code for accurate and reliable solving of industrial flows (Lehmkuhl, O. et al. 2007 ) with special attention on incompressible hypothesis against low Mach compressible flow modeling, as a critic al numerical aspect depending on Reynolds number and gap thickness conditions. In all studied cases a multi-dimensional explicit finite volume fractional-step based algorithm extended to simulate low Mach fluxes using a Runge-Kutta/Crank-Nicholson time integration scheme, with a symmetry preserving discretization has been used. When turbulence modeling is needed, an extension of the WALE (Wall Adapting Local Eddy-viscosity) (Nicoud, F. and Ducros, F., 1999) model to non-structured meshes is applied. The pressure equation is solved by means of parallel Fourier Schur decomposition solver which is an efficient direct solver for loosely coupled PC clusters (Borrell, R. et al. 2011). In a two dimensional periodic way the fluid flow is approach ed by two parallel phenomena (an entrance flow through a channel and a free jet through a surface). In that sense, the present paper is focused on the numeri cal simulation model of the fluid flow through the valve reeds, considering a simplified geometry of an axial hole plus a radial diffuser. The numerical results presented are based on a specific geome try – valve diameter D is 3 times orifice diameter d, while s/d ratio is 0.6 – considering high Reynolds number at the entrance as boundary condition. The studied cases show the influence from laminar to turbulent flow from incompressible assumption to lower subsonic conditions and/or chocked flow. Thu, 18 Apr 2013 13:32:40 GMT http://hdl.handle.net/2117/18868 2013-04-18T13:32:40Z Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Ventosa, Jordi; Pérez Segarra, Carlos David; Oliva Llena, Asensio no The aim of the present paper is to carry out a group of numerical experiments over the fluid flow through the valve reed, using the CFD&HT code TermoFluids, an unstructure d and parallel object-oriented CFD code for accurate and reliable solving of industrial flows (Lehmkuhl, O. et al. 2007 ) with special attention on incompressible hypothesis against low Mach compressible flow modeling, as a critic al numerical aspect depending on Reynolds number and gap thickness conditions. In all studied cases a multi-dimensional explicit finite volume fractional-step based algorithm extended to simulate low Mach fluxes using a Runge-Kutta/Crank-Nicholson time integration scheme, with a symmetry preserving discretization has been used. When turbulence modeling is needed, an extension of the WALE (Wall Adapting Local Eddy-viscosity) (Nicoud, F. and Ducros, F., 1999) model to non-structured meshes is applied. The pressure equation is solved by means of parallel Fourier Schur decomposition solver which is an efficient direct solver for loosely coupled PC clusters (Borrell, R. et al. 2011). In a two dimensional periodic way the fluid flow is approach ed by two parallel phenomena (an entrance flow through a channel and a free jet through a surface). In that sense, the present paper is focused on the numeri cal simulation model of the fluid flow through the valve reeds, considering a simplified geometry of an axial hole plus a radial diffuser. The numerical results presented are based on a specific geome try – valve diameter D is 3 times orifice diameter d, while s/d ratio is 0.6 – considering high Reynolds number at the entrance as boundary condition. The studied cases show the influence from laminar to turbulent flow from incompressible assumption to lower subsonic conditions and/or chocked flow. http://hdl.handle.net/2117/18866 Title: Modular simulation of vapour compression systems with an object oriented tool Authors: Ablanque Mejía, Nicolás; Oliet Casasayas, Carles; Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David Abstract: The objective of this work is to simulate vapour compression refrigeration systems through a modular approach by means of an object - oriented numerical tool called NEST. For this purpose, the global system is modeled as a collection of different elements which are linked between them. Each element represents a specific part of the system (e.g. heat exchanger, compressor, expansion device, tube, cavity, wall, etc.) and can be independently solved for given boundary conditions. The global resolution procedure is carried out by solving all the elements iteratively, transferring information between them, until a converged solution is reached. The system is easily modified by adding, subtracting or substituting any of its elements. This feature gives great flexibility to the model, not only because the configuration of the system can be clearly altered, but also because the numerical model of any element can be easily replaced allowing different levels of simulation. In this work the object - oriented methodology together with the elements description and their resolution procedures are presented. The model is validated against experimental data obtained from a refrigeration cycle working with isobutane. In addition to this, an illustrative case is presented in order to show the system capabilities. Thu, 18 Apr 2013 13:12:59 GMT http://hdl.handle.net/2117/18866 2013-04-18T13:12:59Z Ablanque Mejía, Nicolás; Oliet Casasayas, Carles; Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David no The objective of this work is to simulate vapour compression refrigeration systems through a modular approach by means of an object - oriented numerical tool called NEST. For this purpose, the global system is modeled as a collection of different elements which are linked between them. Each element represents a specific part of the system (e.g. heat exchanger, compressor, expansion device, tube, cavity, wall, etc.) and can be independently solved for given boundary conditions. The global resolution procedure is carried out by solving all the elements iteratively, transferring information between them, until a converged solution is reached. The system is easily modified by adding, subtracting or substituting any of its elements. This feature gives great flexibility to the model, not only because the configuration of the system can be clearly altered, but also because the numerical model of any element can be easily replaced allowing different levels of simulation. In this work the object - oriented methodology together with the elements description and their resolution procedures are presented. The model is validated against experimental data obtained from a refrigeration cycle working with isobutane. In addition to this, an illustrative case is presented in order to show the system capabilities. http://hdl.handle.net/2117/18852 Title: Analysis of the dynamic response of pump-turbine runners. Part I: Experiment Authors: Presas Batlló, Alexandre; Valero Ferrando, M.del Carmen; Huang, Xingxing; Egusquiza Estévez, Eduard; Farhat, Mohamed; Avellan, François Abstract: When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed. Wed, 17 Apr 2013 12:02:49 GMT http://hdl.handle.net/2117/18852 2013-04-17T12:02:49Z Presas Batlló, Alexandre; Valero Ferrando, M.del Carmen; Huang, Xingxing; Egusquiza Estévez, Eduard; Farhat, Mohamed; Avellan, François no When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed. http://hdl.handle.net/2117/18787 Title: PM21 Vibraciones Crepado Marzo 2011-Marzo 2013 Authors: Escaler Puigoriol, Francesc Xavier Mon, 15 Apr 2013 10:20:20 GMT http://hdl.handle.net/2117/18787 2013-04-15T10:20:20Z Escaler Puigoriol, Francesc Xavier no http://hdl.handle.net/2117/18780 Title: Numerical simulation of wind flow around a parabolic trough solar collector Authors: Amine Hachicha, Ahmed; Rodríguez Pérez, Ivette María; Castro González, Jesús; Oliva Llena, Asensio Abstract: The use of parabolic trough solar technology in solar power plants has been increased in recent years. Such devices are located in open terrain and can be the subject of strong winds. As a result, the stability of these devices to track accurately the sun and the convection heat transfer from the receiver tube could be affected. In this paper, a detailed numerical aerodynamic and heat transfer model based on Large Eddy Simulations (LES) modelling for these equipments is presented. First, the model is verified on a circular cylinder in a cross-flow. The drag forces and the heat transfer coefficients are then validated with available experimental measurements. After that, simulations are performed on an Eurotrough solar collector to study the fluid flow and heat transfer around the solar collector and its receiver. Computations are carried out for a Reynolds number of Re W = 3.6 x 10(5) (based on the aperture) and for various pitch angles (h=0,45,90, 135, 80, 270). The aerodynamic coefficients are calculated around the solar collector and validated with measurements performed in wind tunnel tests. Instantaneous velocity field is also studied and compared to aerodynamic coefficients for different pitch angles. The time-averaged flow is characterised by the formation of several recirculation regions around the solar collector and the receiver tube depending on the pitch angle. The study also presents a comparative study of the heat transfer coefficients around the heat collector element with the circular cylinder in a cross-flow and the effect of the pitch angle on the Nusselt number. Fri, 12 Apr 2013 13:17:16 GMT http://hdl.handle.net/2117/18780 2013-04-12T13:17:16Z Amine Hachicha, Ahmed; Rodríguez Pérez, Ivette María; Castro González, Jesús; Oliva Llena, Asensio no The use of parabolic trough solar technology in solar power plants has been increased in recent years. Such devices are located in open terrain and can be the subject of strong winds. As a result, the stability of these devices to track accurately the sun and the convection heat transfer from the receiver tube could be affected. In this paper, a detailed numerical aerodynamic and heat transfer model based on Large Eddy Simulations (LES) modelling for these equipments is presented. First, the model is verified on a circular cylinder in a cross-flow. The drag forces and the heat transfer coefficients are then validated with available experimental measurements. After that, simulations are performed on an Eurotrough solar collector to study the fluid flow and heat transfer around the solar collector and its receiver. Computations are carried out for a Reynolds number of Re W = 3.6 x 10(5) (based on the aperture) and for various pitch angles (h=0,45,90, 135, 80, 270). The aerodynamic coefficients are calculated around the solar collector and validated with measurements performed in wind tunnel tests. Instantaneous velocity field is also studied and compared to aerodynamic coefficients for different pitch angles. The time-averaged flow is characterised by the formation of several recirculation regions around the solar collector and the receiver tube depending on the pitch angle. The study also presents a comparative study of the heat transfer coefficients around the heat collector element with the circular cylinder in a cross-flow and the effect of the pitch angle on the Nusselt number. http://hdl.handle.net/2117/18750 Title: Análisis numérico de la influencia de la fisuración en el comportamiento de una presa de hormigón Authors: Campos, A.; López Garello, Carlos María; Aguado de Cea, Antonio Abstract: This paper introduces a 2D simulation of a cross section of the block 13-14 of Mequinenza Dam, which presents pronounced and uncommon remaining displacements. Joint elements have been included in to the model with a nonlinear constitutive law in order to represent the cracking of concrete. Potential cracking planes defined according with the crack pattern observed in the upstream face were incorporated. The numerical results show how the formation, evolution and opening of a series of horizontal cracks provide much of the observed displacements, thus helping to explain the uncommon behavior detected in the dam. In this study, the influence of fracture parameters such as tensile strength and fracture energy of the joints was considered. En este artículo se presenta una simulación 2D de una sección transversal del bloque 13-14 de la presa de Mequinenza que presenta unos movimientos remanentes acentuados en este bloque. Se ha incluido elementos junta con un comportamiento constitutivo no lineal para representar la fisuración. Se han incorporado en el modelo planos potenciales de fisuración, coincidiendo con algunas juntas de construcción, para lo cual se ha tenido en cuenta un levantamiento detallado de fisuras realizado en paramento aguas arriba de la presa. Los resultados numéricos obtenidos muestran cómo la formación, evolución y apertura de una serie de fisuras horizontales aportan gran parte de los desplazamientos observados en la estructura y permiten explicar de forma consistente el comportamiento diferenciado detectado en la presa. Los trabajos han incluido diversos análisis sobre la influencia de parámetros de fractura, como la resistencia a tracción y la energía de fractura de las juntas. Tue, 09 Apr 2013 18:37:57 GMT http://hdl.handle.net/2117/18750 2013-04-09T18:37:57Z Campos, A.; López Garello, Carlos María; Aguado de Cea, Antonio no Fisuración, Análisis numérico con elementos junta, Presas de hormigón This paper introduces a 2D simulation of a cross section of the block 13-14 of Mequinenza Dam, which presents pronounced and uncommon remaining displacements. Joint elements have been included in to the model with a nonlinear constitutive law in order to represent the cracking of concrete. Potential cracking planes defined according with the crack pattern observed in the upstream face were incorporated. The numerical results show how the formation, evolution and opening of a series of horizontal cracks provide much of the observed displacements, thus helping to explain the uncommon behavior detected in the dam. In this study, the influence of fracture parameters such as tensile strength and fracture energy of the joints was considered. En este artículo se presenta una simulación 2D de una sección transversal del bloque 13-14 de la presa de Mequinenza que presenta unos movimientos remanentes acentuados en este bloque. Se ha incluido elementos junta con un comportamiento constitutivo no lineal para representar la fisuración. Se han incorporado en el modelo planos potenciales de fisuración, coincidiendo con algunas juntas de construcción, para lo cual se ha tenido en cuenta un levantamiento detallado de fisuras realizado en paramento aguas arriba de la presa. Los resultados numéricos obtenidos muestran cómo la formación, evolución y apertura de una serie de fisuras horizontales aportan gran parte de los desplazamientos observados en la estructura y permiten explicar de forma consistente el comportamiento diferenciado detectado en la presa. Los trabajos han incluido diversos análisis sobre la influencia de parámetros de fractura, como la resistencia a tracción y la energía de fractura de las juntas. http://hdl.handle.net/2117/18732 Title: Enhancement in evaluating small group work in courses with large number of students. Machine theory at industrial engineering degrees Authors: Jordi Nebot, Lluïsa; Pàmies Vila, Rosa; Català Calderon, Pau; Puig Ortiz, Joan Tue, 09 Apr 2013 11:49:48 GMT http://hdl.handle.net/2117/18732 2013-04-09T11:49:48Z Jordi Nebot, Lluïsa; Pàmies Vila, Rosa; Català Calderon, Pau; Puig Ortiz, Joan no http://hdl.handle.net/2117/18725 Title: Informe tècnic de la balança 5400 Authors: Trillas i Gay, Enric Abstract: Informe tècnic d'una balança per calibrar manòmetres. Tue, 09 Apr 2013 10:34:35 GMT http://hdl.handle.net/2117/18725 2013-04-09T10:34:35Z Trillas i Gay, Enric no Informe tècnic d'una balança per calibrar manòmetres. http://hdl.handle.net/2117/18703 Title: Informe tècnic de la balança HLG-225-B-1 Authors: Trillas i Gay, Enric Abstract: Informe tècnic de la balança HLG-225-B-1 per a calibrar manòmetres Mon, 08 Apr 2013 13:10:40 GMT http://hdl.handle.net/2117/18703 2013-04-08T13:10:40Z Trillas i Gay, Enric no Informe tècnic de la balança HLG-225-B-1 per a calibrar manòmetres