Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3193
Mon, 16 Oct 2017 22:23:22 GMT2017-10-16T22:23:22ZAn eulerian-lagrangian modeling of fluidized bed
http://hdl.handle.net/2117/106316
An eulerian-lagrangian modeling of fluidized bed
Zhang, Hao; Yuan-Qiang, Tan; Dong-Min, Yang; Trias Miquel, Francesc Xavier; Sheng, Yong; Oliva Llena, Asensio
The particle motions in a fluidized bed were numerically simulated using a Eulerian-Lagrangian model.
The solid phase was modelled via the Discrete Element Method (DEM) while the hydrodynamic model of the fluid
phase was based on the volume-averaged Navier-Stokes equations. A fluid density-based buoyancy (FDB) model was
adopted to calculate the solid-fluid interaction force. In this paper, the complex ‘four way coupled’ interaction as
proposed by Elghobashi in 1991 was modelled, namely the dominant effect of gas phase on the dispersed particles,
the back influence of the particle phase on the gas phase, and interactions between particles such as collision,
agglomeration and break-up. A stable succession of bubble formation and disappearance was captured. Obtained
pressure drop and interparticle contact number had a good agreement with those reported in previous reference
Mon, 10 Jul 2017 11:03:07 GMThttp://hdl.handle.net/2117/1063162017-07-10T11:03:07ZZhang, HaoYuan-Qiang, TanDong-Min, YangTrias Miquel, Francesc XavierSheng, YongOliva Llena, AsensioThe particle motions in a fluidized bed were numerically simulated using a Eulerian-Lagrangian model.
The solid phase was modelled via the Discrete Element Method (DEM) while the hydrodynamic model of the fluid
phase was based on the volume-averaged Navier-Stokes equations. A fluid density-based buoyancy (FDB) model was
adopted to calculate the solid-fluid interaction force. In this paper, the complex ‘four way coupled’ interaction as
proposed by Elghobashi in 1991 was modelled, namely the dominant effect of gas phase on the dispersed particles,
the back influence of the particle phase on the gas phase, and interactions between particles such as collision,
agglomeration and break-up. A stable succession of bubble formation and disappearance was captured. Obtained
pressure drop and interparticle contact number had a good agreement with those reported in previous referenceAdvanced CFD&HT numerical modeling of solar tower receivers
http://hdl.handle.net/2117/106302
Advanced CFD&HT numerical modeling of solar tower receivers
Colomer Rey, Guillem; Chiva Segura, Jorge; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio
This paper presents an advanced methodology for the detailed modeling of the heat transfer and fluid dynamics phenomena in solar tower receivers. It has been carried out in the framework of a more ambitious enterprise which aims at modeling all the complex heat transfer and fluid dynamics phenomena present in central solar receivers. The global model is composed of 4 sub-models (heat conduction, two-phase flow, thermal radiation and natural convection) which are described.
Mon, 10 Jul 2017 09:29:58 GMThttp://hdl.handle.net/2117/1063022017-07-10T09:29:58ZColomer Rey, GuillemChiva Segura, JorgeLehmkuhl Barba, OriolOliva Llena, AsensioThis paper presents an advanced methodology for the detailed modeling of the heat transfer and fluid dynamics phenomena in solar tower receivers. It has been carried out in the framework of a more ambitious enterprise which aims at modeling all the complex heat transfer and fluid dynamics phenomena present in central solar receivers. The global model is composed of 4 sub-models (heat conduction, two-phase flow, thermal radiation and natural convection) which are described.Towards a direct numerical simulation of a lifted CH4-air diffusion flame
http://hdl.handle.net/2117/105953
Towards a direct numerical simulation of a lifted CH4-air diffusion flame
Ventosa Molina, Jordi; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David; Oliva Llena, Asensio
The near field jet of a self-igniting methane-air diffusion jet flame is studied by means of Direct Numerical Simulation (DNS) and a Flamelet/Progress-Variable (FPV) model to include detailed chemistry. Hence, all flow and transport scales are resolved and chemical reactions are assumed to take place in thin layers. Key aspects in the creation of the flamelet database, prior to the DNS simulation, are considered. Inclusion of differential diffusion effects are discussed by analysing the S-shaped curve and autoignition delay times. Similarly, the influence on these parameters of two detailed mechanism, the GRI2.11 and GRI3.0, is assessed. The definition of the progress-variable used in the FPV is analysed and a new definition is proposed. Results of the near jet, up to 20 jet diameters, are shown for the two detailed mechanism.
Wed, 28 Jun 2017 14:21:19 GMThttp://hdl.handle.net/2117/1059532017-06-28T14:21:19ZVentosa Molina, JordiLehmkuhl Barba, OriolPérez Segarra, Carlos DavidOliva Llena, AsensioThe near field jet of a self-igniting methane-air diffusion jet flame is studied by means of Direct Numerical Simulation (DNS) and a Flamelet/Progress-Variable (FPV) model to include detailed chemistry. Hence, all flow and transport scales are resolved and chemical reactions are assumed to take place in thin layers. Key aspects in the creation of the flamelet database, prior to the DNS simulation, are considered. Inclusion of differential diffusion effects are discussed by analysing the S-shaped curve and autoignition delay times. Similarly, the influence on these parameters of two detailed mechanism, the GRI2.11 and GRI3.0, is assessed. The definition of the progress-variable used in the FPV is analysed and a new definition is proposed. Results of the near jet, up to 20 jet diameters, are shown for the two detailed mechanism.A finite-volume/level-set interface capturing method for unstructured grids: Simulations of bubbles rising through viscous liquids
http://hdl.handle.net/2117/105758
A finite-volume/level-set interface capturing method for unstructured grids: Simulations of bubbles rising through viscous liquids
Balcázar Arciniega, Néstor; Jofre Cruanyes, Lluís; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Castro González, Jesús; Oliva Llena, Asensio
A numerical method is developed for simulating two-phase flows with moving inter-phase boundaries, which is integrated in a finite-volume framework on collocated unstructured grids of arbitrary element type. The location, geometry and the movement of the discontinuities are described by the conservative levelset method. The proposed algorithm is validated with experimental results of the buoyant rise of an isolated bubble. Then the method is applied to simulate the interaction between two bubbles during their buoyant rise. Finally, simulations for a set of bubbles with the same diameter initially placed in a random pattern in a periodic cylindrical duct are also carried out. In general, a good agreement is found between the current simulations and results reported in the literature.
Fri, 23 Jun 2017 09:33:15 GMThttp://hdl.handle.net/2117/1057582017-06-23T09:33:15ZBalcázar Arciniega, NéstorJofre Cruanyes, LluísLehmkuhl Barba, OriolRigola Serrano, JoaquimCastro González, JesúsOliva Llena, AsensioA numerical method is developed for simulating two-phase flows with moving inter-phase boundaries, which is integrated in a finite-volume framework on collocated unstructured grids of arbitrary element type. The location, geometry and the movement of the discontinuities are described by the conservative levelset method. The proposed algorithm is validated with experimental results of the buoyant rise of an isolated bubble. Then the method is applied to simulate the interaction between two bubbles during their buoyant rise. Finally, simulations for a set of bubbles with the same diameter initially placed in a random pattern in a periodic cylindrical duct are also carried out. In general, a good agreement is found between the current simulations and results reported in the literature.Conservative discretization of multiphase flow with high density ratios
http://hdl.handle.net/2117/105755
Conservative discretization of multiphase flow with high density ratios
Jofre Cruanyes, Lluís; Lehmkuhl Barba, Oriol; Balcázar Arciniega, Néstor; Castro González, Jesús; Rigola Serrano, Joaquim; Oliva Llena, Asensio
The computation of multiphase flows presenting high density ratios, where the fluids involved are considered immiscible, are of great importance for fundamental physics and industrial applications; such as the study of liquid-gas interfaces, wave motion, simulation of bubbly flows and atomization, injection in diesel engines, chemical processes and others. This work presents and analyzes a collocated and staggered finite-volume mesh discretizations suitable for three-dimensional unstructured meshes, which are able to simulate immiscible multiphase flows with high density ratios. More over, these mesh schemes numerically conserve mass and momentum while minimize errors in the conservation of kinetic energy.
Fri, 23 Jun 2017 09:31:59 GMThttp://hdl.handle.net/2117/1057552017-06-23T09:31:59ZJofre Cruanyes, LluísLehmkuhl Barba, OriolBalcázar Arciniega, NéstorCastro González, JesúsRigola Serrano, JoaquimOliva Llena, AsensioThe computation of multiphase flows presenting high density ratios, where the fluids involved are considered immiscible, are of great importance for fundamental physics and industrial applications; such as the study of liquid-gas interfaces, wave motion, simulation of bubbly flows and atomization, injection in diesel engines, chemical processes and others. This work presents and analyzes a collocated and staggered finite-volume mesh discretizations suitable for three-dimensional unstructured meshes, which are able to simulate immiscible multiphase flows with high density ratios. More over, these mesh schemes numerically conserve mass and momentum while minimize errors in the conservation of kinetic energy.Large eddy simulation model assessment of the turbulent flow through dynamic compressor valves
http://hdl.handle.net/2117/105134
Large eddy simulation model assessment of the turbulent flow through dynamic compressor valves
Estruch Pérez, Olga; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio; Pérez Segarra, Carlos David
The present paper attempts the dynamic simulation of the fluid flow through the valve reed taking into account valve movement due to piston displacement. This work widens previous studies based on numerical experiments with static geometry and constant boundary conditions. Hence, in this work attends the newly in-house implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a three-dimensional explicit finite volume fractional-step algorithm formulated in a second-order, conservative and collocated unstructured grid arrangement.
Large eddy simulation is performed to solve the turbulent flow, using the subgrid scale WALE model. A radial basis function interpolation procedure is used to dynamically move the mesh according with the displacement of the valve. A simplified geometry of an axial hole plus a radial diffuser with a piston based inlet condition is considered. The valve dynamics is assumed to be given by a law according modal analysis of valve reed.
Mon, 05 Jun 2017 15:51:50 GMThttp://hdl.handle.net/2117/1051342017-06-05T15:51:50ZEstruch Pérez, OlgaLehmkuhl Barba, OriolRigola Serrano, JoaquimOliva Llena, AsensioPérez Segarra, Carlos DavidThe present paper attempts the dynamic simulation of the fluid flow through the valve reed taking into account valve movement due to piston displacement. This work widens previous studies based on numerical experiments with static geometry and constant boundary conditions. Hence, in this work attends the newly in-house implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a three-dimensional explicit finite volume fractional-step algorithm formulated in a second-order, conservative and collocated unstructured grid arrangement.
Large eddy simulation is performed to solve the turbulent flow, using the subgrid scale WALE model. A radial basis function interpolation procedure is used to dynamically move the mesh according with the displacement of the valve. A simplified geometry of an axial hole plus a radial diffuser with a piston based inlet condition is considered. The valve dynamics is assumed to be given by a law according modal analysis of valve reed.Hot run test results of a validation optimized water-ice phase change heat accumulator and comparison to numerical analysis¿X¿¿c
http://hdl.handle.net/2117/105102
Hot run test results of a validation optimized water-ice phase change heat accumulator and comparison to numerical analysis¿X¿¿c
Riccius, Jorg; Leiner, Johannes; Castro González, Jesús; Rigola Serrano, Joaquim
Phase change heat accumulators are essential devices for the thermal management of multiple ignition, electric pump driven in-space propulsion systems such as the Low Cost Cryogenic Propulsion (LCCP) system [1], [2]. For Low Temperature Accumulators (LTAs), water/ice is of special interest as phase change material because of its high heat capacity and high latent heat. Therefore, an analysis of the phase change behaviour of both, this heat storage material and an heat transfer medium were performed in the framework of the ISP1 project [2], [3]. In the experiments shown in the current paper, gaseous nitrogen at 80°C
is injected to the inlet of the heat transfer tube. By passing through the heat transfer tube, it causes the heat storage medium ice to melt and the hot nitrogen is cooled down.
The phase change behaviour of the phase change material ice and the heat transfer process from nitrogen to the ice were analysed experimentally in a qualitative and a quantitative way. Finally, the obtained experimental results are compared to the analysis results of theoretical phase-change models carried out by the ISP-1 partner institution UPC [7], [8], [9].
Thu, 01 Jun 2017 15:05:50 GMThttp://hdl.handle.net/2117/1051022017-06-01T15:05:50ZRiccius, JorgLeiner, JohannesCastro González, JesúsRigola Serrano, JoaquimPhase change heat accumulators are essential devices for the thermal management of multiple ignition, electric pump driven in-space propulsion systems such as the Low Cost Cryogenic Propulsion (LCCP) system [1], [2]. For Low Temperature Accumulators (LTAs), water/ice is of special interest as phase change material because of its high heat capacity and high latent heat. Therefore, an analysis of the phase change behaviour of both, this heat storage material and an heat transfer medium were performed in the framework of the ISP1 project [2], [3]. In the experiments shown in the current paper, gaseous nitrogen at 80°C
is injected to the inlet of the heat transfer tube. By passing through the heat transfer tube, it causes the heat storage medium ice to melt and the hot nitrogen is cooled down.
The phase change behaviour of the phase change material ice and the heat transfer process from nitrogen to the ice were analysed experimentally in a qualitative and a quantitative way. Finally, the obtained experimental results are compared to the analysis results of theoretical phase-change models carried out by the ISP-1 partner institution UPC [7], [8], [9].Modelling and experimental validation of the heat accumulator in a Low Trust Cryogenic Propulsion (LTCP) system¿¿e,
http://hdl.handle.net/2117/105100
Modelling and experimental validation of the heat accumulator in a Low Trust Cryogenic Propulsion (LTCP) system¿¿e,
Torras Ortiz, Santiago; Castro González, Jesús; Rigola Serrano, Joaquim; Morales, Sergio; Riccius, Jorg; Leiner, Johannes
The study of one of the components, the heat accumulator, of Low Thrust Cryogenic Propulsion systems (LTCP), is of scientific interest in the framework of ISP-1 project [1]. This device stores thermal energy from the fuel cell that provides electrical energy to the whole system. This thermal energy is employed for the pressurization of the propellant tanks. A numerical model is being developed [2] in order to predict the thermal behaviour of the heat accumulator and having a tool for its design in the next future. The numerical model is validated with experimental results of ISP-1 partners (DLR) [3], [4].
Thu, 01 Jun 2017 12:43:04 GMThttp://hdl.handle.net/2117/1051002017-06-01T12:43:04ZTorras Ortiz, SantiagoCastro González, JesúsRigola Serrano, JoaquimMorales, SergioRiccius, JorgLeiner, JohannesThe study of one of the components, the heat accumulator, of Low Thrust Cryogenic Propulsion systems (LTCP), is of scientific interest in the framework of ISP-1 project [1]. This device stores thermal energy from the fuel cell that provides electrical energy to the whole system. This thermal energy is employed for the pressurization of the propellant tanks. A numerical model is being developed [2] in order to predict the thermal behaviour of the heat accumulator and having a tool for its design in the next future. The numerical model is validated with experimental results of ISP-1 partners (DLR) [3], [4].Experimental and numerical investigation of H2O vapor absorption processes in falling film of LiBr aqueous solution in vertical tubes
http://hdl.handle.net/2117/105085
Experimental and numerical investigation of H2O vapor absorption processes in falling film of LiBr aqueous solution in vertical tubes
Castro González, Jesús; Farnós Baulenas, Joan; García Rivera, Eduardo; Oliva Llena, Asensio
The LiBr-H2O absorption systems are used mainly in large cooling capacity applications (industry, large buildings, etc.), therefore require water from cooling towers to reject heat. However, if middle and low capacity are required (commercial and residential systems), absorption machines should be air-cooled in order to become competitive [1-4].
The absorber represents a major critical component in absorption systems and one of the key issues, in it is the combined heat and mass transfer in the absorption process. For this reason the development of mathematical models for the simulation and experimental data for the validation are always useful tools for the design and improvement of falling film vertical absorbers. A testing device has been designed and built for reproducing absorption phenomena in vertical tubes with the primary objective to obtain experimental data in LiBr-H2O vertical absorbers. The versatility of the experiment allows to obtain a wide range of data.
Wed, 31 May 2017 17:30:56 GMThttp://hdl.handle.net/2117/1050852017-05-31T17:30:56ZCastro González, JesúsFarnós Baulenas, JoanGarcía Rivera, EduardoOliva Llena, AsensioThe LiBr-H2O absorption systems are used mainly in large cooling capacity applications (industry, large buildings, etc.), therefore require water from cooling towers to reject heat. However, if middle and low capacity are required (commercial and residential systems), absorption machines should be air-cooled in order to become competitive [1-4].
The absorber represents a major critical component in absorption systems and one of the key issues, in it is the combined heat and mass transfer in the absorption process. For this reason the development of mathematical models for the simulation and experimental data for the validation are always useful tools for the design and improvement of falling film vertical absorbers. A testing device has been designed and built for reproducing absorption phenomena in vertical tubes with the primary objective to obtain experimental data in LiBr-H2O vertical absorbers. The versatility of the experiment allows to obtain a wide range of data.Large eddy simulation of hydrogen autoignition in a preheated turbulent co-flow
http://hdl.handle.net/2117/105026
Large eddy simulation of hydrogen autoignition in a preheated turbulent co-flow
Muela Castro, Jordi; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio; Ventosa Molina, Jordi
The autoignition process of a hydrogen jet into a preheated turbulent air stream is numerically studied. A Progress-variable (PV) model with the turbulence-chemistry interactions modelled using a Presumed Conditional Moment (PCM) closure has been used. Furthermore, the same case is studied using a Finite Rates model without closure for the reaction rate. The PV-PCM model reproduces satisfactorily the physical behaviour found in the experiments, although the model tends to underpredict the autoignition length. The results of the Finite Rates model also capture accurately the autoignition phenomenology observed experimentally and the autoignition lengths are closer to those obtained in the experiment.
Tue, 30 May 2017 14:35:02 GMThttp://hdl.handle.net/2117/1050262017-05-30T14:35:02ZMuela Castro, JordiLehmkuhl Barba, OriolOliva Llena, AsensioVentosa Molina, JordiThe autoignition process of a hydrogen jet into a preheated turbulent air stream is numerically studied. A Progress-variable (PV) model with the turbulence-chemistry interactions modelled using a Presumed Conditional Moment (PCM) closure has been used. Furthermore, the same case is studied using a Finite Rates model without closure for the reaction rate. The PV-PCM model reproduces satisfactorily the physical behaviour found in the experiments, although the model tends to underpredict the autoignition length. The results of the Finite Rates model also capture accurately the autoignition phenomenology observed experimentally and the autoignition lengths are closer to those obtained in the experiment.