Examinando por Materia "Heat transfer"
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Ítem Accelerated Thermal Simulation for Three-Dimensional Interactive Optimization of Computer Numeric Control Sheet Metal Laser Cutting(American Society of Mechanical Engineers (ASME), 2018-03-01) Mejia D.; Moreno A.; Arbelaiz A.; Posada J.; Ruiz-Salguero O.; Chopitea R.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn the context of computer numeric control (CNC)-based sheet metal laser cutting, the problem of heat transfer simulation is relevant for the optimization of CNC programs. Current physically based simulation tools use numeric or analytic algorithms which provide accurate but slow solutions due to the underlying mathematical description of the model. This paper presents: (1) an analytic solution to the laser heating problem of rectangular sheet metal for curved laser trajectories and convective cooling, (2) a graphics processing unit (GPU) implementation of the analytic solution for fast simulation of the problem, and (3) an integration within an interactive environment for the simulation of sheet metal CNC laser cutting. This analytic approach sacrifices the material removal effect of the laser cut in the favor of an approximated real-time temperature map on the sheet metal. The articulation of thermal, geometric, and graphic feedback in virtual manufacturing environments enables interactive redefinition of the CNC programs for better product quality, lower safety risks, material waste, and energy usage among others. The error with respect to finite element analysis (FEA) in temperature prediction descends as low as 3.5%. Copyright © 2018 by ASME.Ítem Análisis bidimensional axial simétrico de los termoflujos en un tubo de calor(Universidad EAFIT, 2012) Mira Hernández, Carolina; París Londoño, Luis SantiagoÍtem Análisis de la sensibilidad paramétrica y del comportamiento dinámico de la hidrólisis del isocianato de metilo(Centro de Informacion Tecnologica, 2016-01-01) Ojeda, J.C.; GilPavas, E.; Dobrosz-Gómez, I.; Gómez, M.A.; Ojeda, J.C.; GilPavas, E.; Dobrosz-Gómez, I.; Gómez, M.A.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)In this work, parametric sensitivity and dynamic analysis were combined to determine the thermal instability conditions inherent in the methyl isocyanate hydrolysis reaction. This highly exothermic reaction tragically proved to be very sensible to temperature changes in the so-called Bhopal disaster in 1984. A stirred tank reactor in transient state was considered for simulating the reactive system. First, critical operational conditions were defined from the parametric sensitivity analysis. Subsequently, in a rigorous way, the dynamic analysis determined the thermal instability regions, Hopf bifurcations, and the thermal oscillatory behavior of the reactive system. The Matcont® software was used to solve the differential equations set. It was demonstrated that runaway conditions and the periodic solutions of temperature are closely related with the cooling temperature and the dimensionless parameters (f-dimensionless flow and l-heat transfer term) and their critical parameters were obtained: /c=752.39 and fc=1.57.Ítem Appraisal of open software for finite element simulation of 2D metal sheet laser cut(Springer-Verlag France, 2017-08-01) Mejia, D.; Moreno, A.; Ruiz-Salguero, O.; Barandiaran, I.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEFEA simulation of thermal metal cutting is central to interactive design and manufacturing. It is therefore relevant to assess the applicability of FEA open software to simulate 2D heat transfer in metal sheet laser cuts. Application of open source code (e.g. FreeFem++, FEniCS, MOOSE) makes possible additional scenarios (e.g. parallel, CUDA, etc.), with lower costs. However, a precise assessment is required on the scenarios in which open software can be a sound alternative to a commercial one. This article contributes in this regard, by presenting a comparison of the aforementioned freeware FEM software for the simulation of heat transfer in thin (i.e. 2D) sheets, subject to a gliding laser point source. We use the commercial ABAQUS software as the reference to compare such open software. A convective linear thin sheet heat transfer model, with and without material removal is used. This article does not intend a full design of computer experiments. Our partial assessment shows that the thin sheet approximation turns to be adequate in terms of the relative error for linear alumina sheets. Under mesh resolutions better than m , the open and reference software temperature differ in at most 1 of the temperature prediction. Ongoing work includes adaptive re-meshing, nonlinearities, sheet stress analysis and Mach (also called 'relativistic') effects.Ítem Appraisal of open software for finite element simulation of 2D metal sheet laser cut.(Springer-Verlag France, 2016-03-21) Mejia, Daniel; Moreno, Aitor; Ruiz Salguero, Oscar; Barandiaran, Inigo; Universidad EAFIT. Departamento de Ingeniería Mecánica. Grupo de Investigación CAD CAM CAE, Carrera 49 7 Sur-50, Medellín, Colombia.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEFEA simulation of thermal metal cutting is central to interactive design and manufacturing. It is therefore relevant to assess the applicability of FEA open software to simulate 2D heat transfer in metal sheet laser cuts. Application of open source code (e.g. FreeFem++, FEniCS, MOOSE) makes possible additional scenarios (e.g. parallel, CUDA, etc.), with lower costs. However, a precise assessment is required on the scenarios in which open software can be a sound alternative to a commercial one. This article contributes in this regard, by presenting a comparison of the aforementioned freeware FEM software for the simulation of heat transfer in thin (i.e. 2D) sheets, subject to a gliding laser point source. We use the commercial ABAQUS software as the reference to compare such open software. A convective linear thin sheet heat transfer model, with and without material removal is used. This article does not intend a full design of computer experiments. Our partial assessment shows that the thin sheet approximation turns to be adequate in terms of the relative error for linear alumina sheets. Under mesh resolutions better than 10e−5 m , the open and reference software temperature differ in at most 1 % of the temperature prediction. Ongoing work includes adaptive re-meshing, nonlinearities, sheet stress analysis and Mach (also called ‘relativistic’) effects.Ítem Compendium of publications on: differential operators on manifolds for CAD CAM CAE and computer graphics(Universidad EAFIT, 2020) Mejía Parra, Daniel; Ruiz Salguero, Oscar Eduardo; Posada Velásquez, Jorge LeónThis Doctoral Thesis develops novel articulations of Differential Operators on Manifolds for applications on Computer Aided Design, Manufacture and Computer Graphics, as follows: (1) Mesh Parameterization and Segmentation. Development and application of Laplace-Beltrami, Hessian, Geodesic and Curvature operators for topology and geometry – driven segmentations and parameterizations of 2-manifold triangular meshes. Applications in Reverse Engineering, Manufacturing and Medicine. (2) Computing of Laser-driven Temperature Maps in thin plates. Spectral domain - based analytic solutions of the transient, non-homogeneous heat equation for simulation of temperature maps in multi-laser heated thin plates, modeled as 2-manifolds plus thickness. (3) Real-time estimation of dimensional compliance of hot out-of-forge workpieces. A Special Orthogonal SO(3) transformation between 2-manifolds is found, which enables a distance operator between 2-manifolds in R^3 (or m-manifolds in R^n). This process instruments the real-time assessment of dimensional compliance of hot workpieces, in the factory floor shop. (4) Slicing or Level-Set computation for 2-manifold triangular meshes in Additive Manufacturing. Development of a classification of non-degenerate (i.e. non-singular Hessian) and degenerate (i.e. singular Hessian) critical points of non-Morse functions on 2-manifold objects, followed by computation of level sets for Additive Manufacturing. Most of the aforementioned contributions have been screened and accepted by the international scientific community (and published). Non-published material corresponds to confidential developments which are commercially exploited by the sponsors and therefore banned from dissemination.Ítem Desarrollo de una metodología para síntesis, optimización y diagnóstico de redes de transferencia de calor (HEN) – tratamiento de problemas con corrientes isotérmicas(2009-10) Jaramillo Chica, Esteban; Sánchez Cossio, Javier Arley; Acosta Maya, Diego AndrésÍtem Dynamic analysis of heat transfer through a fin of constant cross-sectional area: Specified fin tip temperature(2009-01-01) Carranza, R.G.; Ospina Giraldo, J.F.; Carranza, R.G.; Ospina Giraldo, J.F.; Universidad EAFIT. Departamento de Ciencias; Lógica y ComputaciónA dynamic analysis is performed for heat transfer through a fin with constant cross-sectional area and with a specified fin tip temperature. The process starts with a dynamic energy balance around the fin. Laplace transforms and the Bromwich Integral are used to solve analytically the resulting partial differential equation. The final purely analytical solution is compared to the well known steady state solution. The two match exactly as time approaches infinity. Furthermore it is shown that the steady-state and dynamic characteristics of the fin are directly tied to the Biot number. Copyright © 2009 by ASME.Ítem Fast analytic simulation for multi-laser heating of sheet metal in GPU(MDPI AG, 2018-11-01) Mejia-Parra D.; Montoya-Zapata D.; Arbelaiz A.; Moreno A.; Posada J.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEInteractive multi-beam laser machining simulation is crucial in the context of tool path planning and optimization of laser machining parameters. Current simulation approaches for heat transfer analysis (1) rely on numerical Finite Element methods (or any of its variants), non-suitable for interactive applications; and (2) require the multiple laser beams to be completely synchronized in trajectories, parameters and time frames. To overcome this limitation, this manuscript presents an algorithm for interactive simulation of the transient temperature field on the sheet metal. Contrary to standard numerical methods, our algorithm is based on an analytic solution in the frequency domain, allowing arbitrary time/space discretizations without loss of precision and non-monotonic retrieval of the temperature history. In addition, the method allows complete asynchronous laser beams with independent trajectories, parameters and time frames. Our implementation in a GPU device allows simulations at interactive rates even for a large amount of simultaneous laser beams. The presented method is already integrated into an interactive simulation environment for sheet cutting. Ongoing work addresses thermal stress coupling and laser ablation. © 2018 by the authors.Ítem A FIRST-ORDER TIME CONSTANT ESTIMATION FOR NONLINEAR DIFFUSION PROBLEMS(TAYLOR & FRANCIS INC, 2014-06-03) Simon, Laurent; Ospina, Juan; Simon, Laurent; Ospina, Juan; Universidad EAFIT. Departamento de Ciencias; Lógica y ComputaciónA Laplace transform-based procedure was proposed to calculate the effective time constant for a class of nonlinear diffusion problems. The governing mathematical representation was first estimated with a linear model by omitting the nonlinear term. The solution to this problem was later introduced into the original equation, which was solved with Laplace transforms, resulting in a first-order approximation of the real system's behavior. A time constant was calculated using frequency-domain expressions. Two case studies were considered to illustrate the methodology. As the rate of heat supplied to a rod is raised, the speed at which the temperature reached an equilibrium value decreased. Increasing the maximum velocity in reaction-diffusion transport by a factor of three lowered the time constant by only 1.7%. The applications of this method range from biosensor dynamics to process control. © 2014 Copyright Taylor and Francis Group, LLC.Ítem Frequency-domain analytic method for efficient thermal simulation under curved trajectories laser heating(Elsevier BV, 2019-01-01) Mejia-Parra D.; Moreno A.; Posada J.; Ruiz-Salguero O.; Barandiaran I.; Poza J.C.; Chopitea R.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn the context of Computer Simulation, the problem of heat transfer analysis of thin plate laser heating is relevant for downstream simulations of machining processes. Alternatives to address the problem include (i) numerical methods, which require unaffordable time and storage computing resources even for very small domains, (ii) analytical methods, which are less expensive but are limited to simple geometries, straight trajectories and do not account for material non-linearities or convective cooling. This manuscript presents a parallel efficient analytic method to determine, in a thin plate under convective cooling, the transient temperature field resulting from application of a laser spot following a curved trajectory. Convergence of both FEA (Finite Element Analysis) and the analytic approaches for a small planar plate is presented, estimating a maximum relative error for the analytic approach below 3.5% at the laser spot. Measured computing times evidence superior efficiency of the analytic approach w.r.t. FEA. A study case, with the analytic solution, for a large spatial and time domain (1m×1m and 12s history, respectively) is presented. This case is not tractable with FEA, where domains larger than 0.05m×0.05m and 2s require high amounts of computing time and storage. © 2019 International Association for Mathematics and Computers in Simulation (IMACS)Ítem Hybrid geometry / topology based mesh segmentation for reverse engineering(PERGAMON-ELSEVIER SCIENCE LTD, 2018-06-01) Mejia D.; Ruiz-Salguero O.; Sánchez J.R.; Posada J.; Moreno A.; Cadavid C.A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEMesh segmentation and parameterization are crucial for Reverse Engineering (RE). Bijective parameterizations of the sub-meshes are a sine-qua-non test for segmentation. Current segmentation methods use either (1) topologic or (2) geometric criteria to partition the mesh. Reported topology-based segmentations produce large sub-meshes which reject parameterizations. Geometry-based segmentations are very sensitive to local variations in dihedral angle or curvatures, thus producing an exaggerated large number of small sub-meshes. Although small sub-meshes accept nearly isometric parameterizations, this significant granulation defeats the intent of synthesizing a usable Boundary Representation (compulsory for RE). In response to these limitations, this article presents an implementation of a hybrid geometry / topology segmentation algorithm for mechanical workpieces. This method locates heat transfer constraints (topological criterion) in low frequency neighborhoods of the mesh (geometric criterion) and solves for the resulting temperature distribution on the mesh. The mesh partition dictated by the temperature scalar map results in large, albeit parameterizable, sub-meshes. Our algorithm is tested with both benchmark repository and physical piece scans data. The experiments are successful, except for the well - known cases of topological cylinders, which require a user - introduced boundary along the cylinder generatrices. © 2018 Elsevier LtdÍtem Hybrid geometry / topology based mesh segmentation for reverse engineering(PERGAMON-ELSEVIER SCIENCE LTD, 2018-06-01) Mejia D.; Ruiz-Salguero O.; Sánchez J.R.; Posada J.; Moreno A.; Cadavid C.A.; Mejia D.; Ruiz-Salguero O.; Sánchez J.R.; Posada J.; Moreno A.; Cadavid C.A.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesMesh segmentation and parameterization are crucial for Reverse Engineering (RE). Bijective parameterizations of the sub-meshes are a sine-qua-non test for segmentation. Current segmentation methods use either (1) topologic or (2) geometric criteria to partition the mesh. Reported topology-based segmentations produce large sub-meshes which reject parameterizations. Geometry-based segmentations are very sensitive to local variations in dihedral angle or curvatures, thus producing an exaggerated large number of small sub-meshes. Although small sub-meshes accept nearly isometric parameterizations, this significant granulation defeats the intent of synthesizing a usable Boundary Representation (compulsory for RE). In response to these limitations, this article presents an implementation of a hybrid geometry / topology segmentation algorithm for mechanical workpieces. This method locates heat transfer constraints (topological criterion) in low frequency neighborhoods of the mesh (geometric criterion) and solves for the resulting temperature distribution on the mesh. The mesh partition dictated by the temperature scalar map results in large, albeit parameterizable, sub-meshes. Our algorithm is tested with both benchmark repository and physical piece scans data. The experiments are successful, except for the well - known cases of topological cylinders, which require a user - introduced boundary along the cylinder generatrices. © 2018 Elsevier LtdÍtem Improvement of a knock model for natural gas SI engines through heat transfer evaluation(Springer-Verlag France, 2018-11-01) Sierra Parra A.F.; Díaz Torres A.G.; Sierra Parra A.F.; Díaz Torres A.G.; Universidad EAFIT. Departamento de Ingeniería de Producción; Ingeniería, Energía, Exergía y Sostenibilidad (IEXS)Knock is an abnormal combustion phenomena capable of causing serious damage to spark ignition engines, and is a constraint to reach the maximum potential of the engine, since strategies to increase power output and improve efficiency such as turbocharging, increased compression ratio and the advancement of spark timing, also increase the possibility of knock occurrence. Therefore, it is crucial to take into account the limits imposed by knock in the design and operating conditions of the engine when using an engine computational model. In this article a zero-dimensional two-zone engine model, coupled with a chemical kinetic model for knock detection through end-gas auto-ignition is developed and validated, for a natural gas engine. Given the importance of an accurate knock prediction, five heat transfer coefficient correlations are compared to find the most suitable to predict the knock occurrence, through calculation of a knock criterion. Correlations from Sitkei and Annand were the most suitable to predict this knock criterion for the experimental data used, and the Sitkei correlation was later tested in a parametric study to predict the effect of spark timing, compression ratio, equivalence ratio and inlet temperature in knock occurrence and intensity. Results were in accordance with real engine behaviour when knock occurs. © 2017, Springer-Verlag France SAS, part of Springer Nature.Ítem Optimizing performance in spark ignition engines with simulation metamodels(Springer-Verlag France, 2019-01-01) Zutta E.; Acosta D.; Diaz G.; Zutta E.; Acosta D.; Diaz G.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)This work develops a systematic methodology able to identify the desired work points, the metamodels were evaluated varying air–fuel ratio, ignition timing, compression ratio, and combustion duration using design of computer experiments and RSM. It provide the possibility to determine optimal control parameters, according to selected objectives and operating constraints. This methodology is able to automatically identify the optimal engine calibration with less computational effort. Only in this way, the reliability of an integrated metamodel/optimizer approach can be included in a general-purpose that is to identify the engine calibration that minimizes motor vehicle emissions according to European emission standards (European Union in Off J Eur Union 50, 2007). As long as it improves mean effective pressure and reduces exergy destruction due to heat transfer and combustion process. Since, in internal combustion engines, more than 30–40 % of fuel energy wastes through the exhaust and just 12–25 % of the fuel energy converts to useful work. So, researchers are motivated to recover the heat from the waste sources in engines using the ways which not only reduce the demand of fossil fuels, but also reduce the harmful greenhouse gases and help to energy saving (Hatami et al. in Neural Comput Appl 25(7–8):2079–2090, 2014). The advantages of this contribution include the ability to study a wide range of parametric space and to independently evaluate physical and chemical processes, and detailed in-cylinder information, which is normally not available or is inaccessible in experiments. The uncertainty of the information in this unexplored design region can be quantified. Finally, the problem of optimizing involves three optimization fronts, energetic, economic and ecological (Chica and Torres in Int J Interact Des Manuf 12(1):355–392, 2018). © 2019, Springer-Verlag France SAS, part of Springer Nature.Ítem Optimizing performance in spark ignition engines with simulation metamodels(Springer-Verlag France, 2019-01-01) Zutta E.; Acosta D.; Diaz G.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosThis work develops a systematic methodology able to identify the desired work points, the metamodels were evaluated varying air–fuel ratio, ignition timing, compression ratio, and combustion duration using design of computer experiments and RSM. It provide the possibility to determine optimal control parameters, according to selected objectives and operating constraints. This methodology is able to automatically identify the optimal engine calibration with less computational effort. Only in this way, the reliability of an integrated metamodel/optimizer approach can be included in a general-purpose that is to identify the engine calibration that minimizes motor vehicle emissions according to European emission standards (European Union in Off J Eur Union 50, 2007). As long as it improves mean effective pressure and reduces exergy destruction due to heat transfer and combustion process. Since, in internal combustion engines, more than 30–40 % of fuel energy wastes through the exhaust and just 12–25 % of the fuel energy converts to useful work. So, researchers are motivated to recover the heat from the waste sources in engines using the ways which not only reduce the demand of fossil fuels, but also reduce the harmful greenhouse gases and help to energy saving (Hatami et al. in Neural Comput Appl 25(7–8):2079–2090, 2014). The advantages of this contribution include the ability to study a wide range of parametric space and to independently evaluate physical and chemical processes, and detailed in-cylinder information, which is normally not available or is inaccessible in experiments. The uncertainty of the information in this unexplored design region can be quantified. Finally, the problem of optimizing involves three optimization fronts, energetic, economic and ecological (Chica and Torres in Int J Interact Des Manuf 12(1):355–392, 2018). © 2019, Springer-Verlag France SAS, part of Springer Nature.Ítem Región de Inestabilidad y Optimización de las Condiciones de Producción de Metanol en un Reactor Lurgi(Centro de Informacion Tecnologica, 2016-01-01) Gómez, M.Á.; Dobrosz-Gómez, I.; Gilpavas, E.; Gómez, M.Á.; Dobrosz-Gómez, I.; Gilpavas, E.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)In the present work, the operational conditions for methanol synthesis in a Lurgi reactor are analyzed. The industrial data for a packed reactor (consisting of 1620 tubes of 7 m long) are the basis of this study. At first, the industrial reactor is simulated achieving excellent agreement with plant data. Then, the instability region is defined as a boundary in the conversion-temperature diagram and defines the conditions that must be avoided during reactor operation. The optimization of the operational conditions is performed based on the optimal temperature progression from the iso-reaction rate curves. Finally, it was found that the cooling fluid must be at 230 °C and that the heat transfer coefficient must guarantee a value of 118 J/(s.K.m2).Ítem Thermal and permeability properties of metal Aluminum foams for functional applications(Pontificia Universidad Javeriana, 2017-01-01) Fernández-Morales, P.; Cano-Montoya, C.A.; Pérez-Mesa, J.A.; Navacerrada, M.Á.; Universidad EAFIT. Departamento de Geología; Ciencias del MarTo determine the coefficients of permeability and thermal conductivity of aluminum metal foams, thermal transference and pressure drop tests were carried out. Metal foam samples measuring 50 mm in diameter and 20 mm in thickness with pore sizes ranging between 0.5 and 2.0 mm were used for both tests. An adaptation in a fluid flow system was made to perform the pressure drop tests, and Darcy’s law was used to calculate the permeability values. A thermal box test and Fourier’s law were used to obtain the conductivity coefficients. The results showed that the pore size has an important influence on the values of permeability and thermal conductivity. Finally, the results were compared with those reported by other researchers and were found to be consistent with those found in previous work. Our interest is to enhance knowledge regarding aluminum metal foams and show their potential use in applications that involve fluid flow and heat transfer. © 2017, Pontificia Universidad Javeriana. All rights reserved.