Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/184779
Sat, 20 Jul 2024 00:27:56 GMT2024-07-20T00:27:56ZOn the validation of numerical simulation with experimental results on compressible turbulent flow in an inertial particle separator device
http://hdl.handle.net/2117/412128
On the validation of numerical simulation with experimental results on compressible turbulent flow in an inertial particle separator device
Bahramian, Linda; Amani, Ahmad; Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Pérez Segarra, Carlos David
To remove particles from entering the engine or Environmental Control System (ECS), an Inertial Particle Separator (IPS) can be situated in the intake. In IPS, a rapid change in flow direction is induced, and particles separate from the core outlet because of their inertia. Small particles with a low Stokes number (St) follow the flow and often enter the core outlet, while the large particles with a high St are thrown into the scavenge by their high inertia. Accurately capturing the unsteadiness of the fluid is crucial, especially with low scavenge mass flow fraction for the particles with low St. The numerical simulation of the compressible flow is validated here, implementing the 3D Improved Delayed Detached Eddy Simulation (IDDES) and the Reynolds-averaged Navier-Stokes (RANS) methods against experimental data. It is shown that the IDDES method can capture correctly the unsteadiness of the flow. After validation of the fluid phase, the particle separation efficiency was studied for different particle diameters using these turbulence numerical methods along with three different ambient temperatures: standard, hot, and cold. The separation efficiency values were in agreement with the experimental data.
Fri, 19 Jul 2024 10:55:03 GMThttp://hdl.handle.net/2117/4121282024-07-19T10:55:03ZBahramian, LindaAmani, AhmadRigola Serrano, JoaquimOliet Casasayas, CarlesPérez Segarra, Carlos DavidTo remove particles from entering the engine or Environmental Control System (ECS), an Inertial Particle Separator (IPS) can be situated in the intake. In IPS, a rapid change in flow direction is induced, and particles separate from the core outlet because of their inertia. Small particles with a low Stokes number (St) follow the flow and often enter the core outlet, while the large particles with a high St are thrown into the scavenge by their high inertia. Accurately capturing the unsteadiness of the fluid is crucial, especially with low scavenge mass flow fraction for the particles with low St. The numerical simulation of the compressible flow is validated here, implementing the 3D Improved Delayed Detached Eddy Simulation (IDDES) and the Reynolds-averaged Navier-Stokes (RANS) methods against experimental data. It is shown that the IDDES method can capture correctly the unsteadiness of the flow. After validation of the fluid phase, the particle separation efficiency was studied for different particle diameters using these turbulence numerical methods along with three different ambient temperatures: standard, hot, and cold. The separation efficiency values were in agreement with the experimental data.Experimental and numerical pressure drop investigation of a protruding tube microchannel heat exchanger
http://hdl.handle.net/2117/412082
Experimental and numerical pressure drop investigation of a protruding tube microchannel heat exchanger
Settati, Mohamed; Oliet Casasayas, Carles; Sanmartí Perona, Oriol; Oliva Llena, Asensio
An experimental and numerical fluid flow study in a micro heat exchanger (microHEX) is conducted in this work to investigate its pressure drop characteristics. The microHEX sample presents a high degree of protrusion of the microchannels inside the inlet and outlet manifolds (Lprot /Dm =0.7), a large manifold-to-branch area aspect ratio (Am/As =37), and a very small flow division in each microchannel (ß=1/34). These features configure T-junctions that differ completely from the conventional ones in the literature. Experimental measurements of the microHEX pressure drop were performed for the Reynolds range of 300-2200. The numerical methodology combines a 1D model to evaluate the pressure drop of a single microchannel, adding minor entrance and exit losses due to the change of section and direction. A CFD numerical simulation evaluates the particular pressure loss associated with the dividing T-junction towards the protruded microchannel. The numerical simulation pressure drop results compared well with the experimental measurements, reporting a difference of 3.11% for an initial case. An extension of the work will soon cover all the collected experimental cases.
Fri, 19 Jul 2024 07:26:53 GMThttp://hdl.handle.net/2117/4120822024-07-19T07:26:53ZSettati, MohamedOliet Casasayas, CarlesSanmartí Perona, OriolOliva Llena, AsensioAn experimental and numerical fluid flow study in a micro heat exchanger (microHEX) is conducted in this work to investigate its pressure drop characteristics. The microHEX sample presents a high degree of protrusion of the microchannels inside the inlet and outlet manifolds (Lprot /Dm =0.7), a large manifold-to-branch area aspect ratio (Am/As =37), and a very small flow division in each microchannel (ß=1/34). These features configure T-junctions that differ completely from the conventional ones in the literature. Experimental measurements of the microHEX pressure drop were performed for the Reynolds range of 300-2200. The numerical methodology combines a 1D model to evaluate the pressure drop of a single microchannel, adding minor entrance and exit losses due to the change of section and direction. A CFD numerical simulation evaluates the particular pressure loss associated with the dividing T-junction towards the protruded microchannel. The numerical simulation pressure drop results compared well with the experimental measurements, reporting a difference of 3.11% for an initial case. An extension of the work will soon cover all the collected experimental cases.A 3D symmetry-preserving simulation of a concentrated photovoltaic thermal (CPVT) solar collector
http://hdl.handle.net/2117/410331
A 3D symmetry-preserving simulation of a concentrated photovoltaic thermal (CPVT) solar collector
Santos Serrano, Daniel; Rigola Serrano, Joaquim; Castro González, Jesús; Trias Miquel, Francesc Xavier
In this work, a general collocated and unconditionally stable framework on unstructured meshes for solving Conjugate Heat Transfer (CHT) problems is presented by means of preserving the underlying symmetries of the continuous differential operators, thus not introducing uncontrolled artificial numerical dissipation to our system. Then, this framework is applied to solve a Concentrated PhotoVoltaic Thermal (CPVT) Solar Collector. Furthermore, a new boundary condition is implemented to consider the heat transfer between enclosed elements, including radiation. The model is validated using experimental data.
Thu, 20 Jun 2024 15:34:59 GMThttp://hdl.handle.net/2117/4103312024-06-20T15:34:59ZSantos Serrano, DanielRigola Serrano, JoaquimCastro González, JesúsTrias Miquel, Francesc XavierIn this work, a general collocated and unconditionally stable framework on unstructured meshes for solving Conjugate Heat Transfer (CHT) problems is presented by means of preserving the underlying symmetries of the continuous differential operators, thus not introducing uncontrolled artificial numerical dissipation to our system. Then, this framework is applied to solve a Concentrated PhotoVoltaic Thermal (CPVT) Solar Collector. Furthermore, a new boundary condition is implemented to consider the heat transfer between enclosed elements, including radiation. The model is validated using experimental data.Parametric study of structured thermocline storage systems
http://hdl.handle.net/2117/406390
Parametric study of structured thermocline storage systems
Vera i Fernández, Jordi; Sanmartí Perona, Oriol; Torras Ortiz, Santiago; Pérez Segarra, Carlos David
A thermal accumulator system for concentrated solar power is modeled to perform a parametric study. The thermal accumulation system is a type of structured thermocline where there is a solid filler material with some channels where the heat transfer fluid (HTF) circulates. The energy is accumulated in both the HFT (a molten salt) and the solid (a ceramic material). The model considers a simplified 3D domain for the solid, considering a single channel and taking advantage of the symmetries of the problem. For the fluid, a 1D step-by-step discretization is used, and the solid and fluid are coupled using a conjugate heat transfer (CHT) approach. The studied parameters are geometrical parameters (tank diameter, tank height, channel diameter, distance between channels, and channels arrangement) and operational parameters (charge and discharge cycles criteria, mass flow rates).
Thu, 11 Apr 2024 13:58:08 GMThttp://hdl.handle.net/2117/4063902024-04-11T13:58:08ZVera i Fernández, JordiSanmartí Perona, OriolTorras Ortiz, SantiagoPérez Segarra, Carlos DavidA thermal accumulator system for concentrated solar power is modeled to perform a parametric study. The thermal accumulation system is a type of structured thermocline where there is a solid filler material with some channels where the heat transfer fluid (HTF) circulates. The energy is accumulated in both the HFT (a molten salt) and the solid (a ceramic material). The model considers a simplified 3D domain for the solid, considering a single channel and taking advantage of the symmetries of the problem. For the fluid, a 1D step-by-step discretization is used, and the solid and fluid are coupled using a conjugate heat transfer (CHT) approach. The studied parameters are geometrical parameters (tank diameter, tank height, channel diameter, distance between channels, and channels arrangement) and operational parameters (charge and discharge cycles criteria, mass flow rates).Optimized approach for CFD simulations of HVAC systems with grill air diffusers
http://hdl.handle.net/2117/406346
Optimized approach for CFD simulations of HVAC systems with grill air diffusers
Vera i Fernández, Jordi; Schillaci, Eugenio; Rigola Serrano, Joaquim; Oliet Casasayas, Carles
A proper CFD simulation of air distribution within a room requires the correct representation of inlet conditions from ventilation grids. Those elements are usually characterized by blades with a certain inclination angle or even by a curvature, whose correct representation by finite volumes approaches requires the employment of very fine meshes. The coupling of those fine inlet domains with the coarser mesh of the environment can lead to unacceptable costs for common computational resources. In this work, an optimized methodology is presented to simulate the inlet flow conditions of an air diffuser within a bigger environment, like a room or a transport vehicle cabin. The method aims at reducing the computational cost of CFD simulations, by solving the velocity field of the diffuser in a local domain, and then mapping this velocity to the surrounding domain. Additionally, this allows us to solve the diffuser only once and reuse the velocity field multiple times for different room configurations.
Wed, 10 Apr 2024 18:05:31 GMThttp://hdl.handle.net/2117/4063462024-04-10T18:05:31ZVera i Fernández, JordiSchillaci, EugenioRigola Serrano, JoaquimOliet Casasayas, CarlesA proper CFD simulation of air distribution within a room requires the correct representation of inlet conditions from ventilation grids. Those elements are usually characterized by blades with a certain inclination angle or even by a curvature, whose correct representation by finite volumes approaches requires the employment of very fine meshes. The coupling of those fine inlet domains with the coarser mesh of the environment can lead to unacceptable costs for common computational resources. In this work, an optimized methodology is presented to simulate the inlet flow conditions of an air diffuser within a bigger environment, like a room or a transport vehicle cabin. The method aims at reducing the computational cost of CFD simulations, by solving the velocity field of the diffuser in a local domain, and then mapping this velocity to the surrounding domain. Additionally, this allows us to solve the diffuser only once and reuse the velocity field multiple times for different room configurations.DNS and RANS simulations of a coil heat exchanger immersed in a tank
http://hdl.handle.net/2117/406345
DNS and RANS simulations of a coil heat exchanger immersed in a tank
Vera i Fernández, Jordi; Torras Ortiz, Santiago; Schillaci, Eugenio; Oliva Llena, Asensio
The operation of heat exchangers in a thermal system can be described by simple heat transfer equations. The heat exchange is normally defined by a global heat transfer coefficient, which takes into account internal and external convection and the characteristics of the pipe. This coefficient can be obtained analytically only for heat exchangers with standard and simple geometric characteristics otherwise leading to unacceptable inaccuracies when employed in lower-order models. An effective solution for calculating the global heat transfer coefficient for a particular heat exchanger consists of the full simulation of the heat exchange, including internal pipes and external fluid, through CFD&HT simulations. In this work, simulations of a coil heat exchanger are carried out, and the values obtained are compared with those of a reference work obtained experimentally [1]. In this work, the results obtained by means of different turbulence models present in the OpenFOAM software are compared.
Wed, 10 Apr 2024 17:37:19 GMThttp://hdl.handle.net/2117/4063452024-04-10T17:37:19ZVera i Fernández, JordiTorras Ortiz, SantiagoSchillaci, EugenioOliva Llena, AsensioThe operation of heat exchangers in a thermal system can be described by simple heat transfer equations. The heat exchange is normally defined by a global heat transfer coefficient, which takes into account internal and external convection and the characteristics of the pipe. This coefficient can be obtained analytically only for heat exchangers with standard and simple geometric characteristics otherwise leading to unacceptable inaccuracies when employed in lower-order models. An effective solution for calculating the global heat transfer coefficient for a particular heat exchanger consists of the full simulation of the heat exchange, including internal pipes and external fluid, through CFD&HT simulations. In this work, simulations of a coil heat exchanger are carried out, and the values obtained are compared with those of a reference work obtained experimentally [1]. In this work, the results obtained by means of different turbulence models present in the OpenFOAM software are compared.Assessment of LES models for a fully developed windturbine array boundary layer
http://hdl.handle.net/2117/403765
Assessment of LES models for a fully developed windturbine array boundary layer
Folch Flórez, David; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
Direct numerical simulations of the incompressible Navier-Stokes equations at high Reynolds numbers are not yet feasible, so dynamically less complex mathematical formulations such as Large Eddy Simulation (LES) have been developed. For the well-known eddy-viscosity models for LES, the computational method is based on the combination of invariants of a symmetric tensor that depends on the gradient of the resolved velocity field, G=¿u. Several models (namely S3PQR) have been developed using the first three principal invariants of the symmetric tensor GGT with excellent results. Therefore, in this work, we will focus on the application of the S3PQR and other LES models on the free boundary layer case. Then, we will test their performances over a fully developed boundary layer wind farm, using a simplified model of a wind turbine.
Tue, 05 Mar 2024 18:56:51 GMThttp://hdl.handle.net/2117/4037652024-03-05T18:56:51ZFolch Flórez, DavidTrias Miquel, Francesc XavierOliva Llena, AsensioDirect numerical simulations of the incompressible Navier-Stokes equations at high Reynolds numbers are not yet feasible, so dynamically less complex mathematical formulations such as Large Eddy Simulation (LES) have been developed. For the well-known eddy-viscosity models for LES, the computational method is based on the combination of invariants of a symmetric tensor that depends on the gradient of the resolved velocity field, G=¿u. Several models (namely S3PQR) have been developed using the first three principal invariants of the symmetric tensor GGT with excellent results. Therefore, in this work, we will focus on the application of the S3PQR and other LES models on the free boundary layer case. Then, we will test their performances over a fully developed boundary layer wind farm, using a simplified model of a wind turbine.Strategies for increasing the arithmetic intensity on ensemble averaged parallel-in-time simulations
http://hdl.handle.net/2117/403762
Strategies for increasing the arithmetic intensity on ensemble averaged parallel-in-time simulations
Plana Riu, Josep; Trias Miquel, Francesc Xavier; Alsalti Baldellou, Àdel; Oliva Llena, Asensio
Extracting flow statistics from flow simulations requires generally long in- tegration intervals in which a good deal of the time is spent time-averaging the results. In order to avoid this, ensemble averaging can be applied to reduce the overall simulation time by simulating multiple statistically independent flow states for a smaller period of time and later averaging among them. In order to optimize the process, a cross-platform portable parallel-in-time method is presented in which the overall simulation is solved making use of sparse matrix-matrix products (SpMM), a high arithmetic intensity counterpart for sparse matrix-vector products, so that the efficiency of the simulation is increased.
Tue, 05 Mar 2024 18:27:24 GMThttp://hdl.handle.net/2117/4037622024-03-05T18:27:24ZPlana Riu, JosepTrias Miquel, Francesc XavierAlsalti Baldellou, ÀdelOliva Llena, AsensioExtracting flow statistics from flow simulations requires generally long in- tegration intervals in which a good deal of the time is spent time-averaging the results. In order to avoid this, ensemble averaging can be applied to reduce the overall simulation time by simulating multiple statistically independent flow states for a smaller period of time and later averaging among them. In order to optimize the process, a cross-platform portable parallel-in-time method is presented in which the overall simulation is solved making use of sparse matrix-matrix products (SpMM), a high arithmetic intensity counterpart for sparse matrix-vector products, so that the efficiency of the simulation is increased.Combustion and air flows simulations of an industrial kiln for sanitary ware manufacture
http://hdl.handle.net/2117/403750
Combustion and air flows simulations of an industrial kiln for sanitary ware manufacture
Liu, Jiannan; Ruano Pérez, Jesús; Schillaci, Eugenio; Rigola Serrano, Joaquim; Pérez Segarra, Carlos David
The implementation of green hydrogen as fuel in industrial kilns, such as those required in ceramic ware manufacturing processes, would be a disruptive milestone in the decarbonization process of the energyintensive industry. In this research, the design of new green combustion technology furnaces is supported by two types of simulations: i) local simulation of combustors with different fuel mixtures; and ii) global simulation of air currents inside the kiln to study and optimize their distribution. In the current paper, different simulations of the combustor using different CH4-H2 mixtures are proposed, while preliminary air-flow simulations of the kiln are set and compared against a 1D thermodynamic model of the same system in terms of mean temperatures and mass flows. In the next steps of the project, local combustors results will be employed as input data for the global simulation of kiln air distribution.
Tue, 05 Mar 2024 15:30:51 GMThttp://hdl.handle.net/2117/4037502024-03-05T15:30:51ZLiu, JiannanRuano Pérez, JesúsSchillaci, EugenioRigola Serrano, JoaquimPérez Segarra, Carlos DavidThe implementation of green hydrogen as fuel in industrial kilns, such as those required in ceramic ware manufacturing processes, would be a disruptive milestone in the decarbonization process of the energyintensive industry. In this research, the design of new green combustion technology furnaces is supported by two types of simulations: i) local simulation of combustors with different fuel mixtures; and ii) global simulation of air currents inside the kiln to study and optimize their distribution. In the current paper, different simulations of the combustor using different CH4-H2 mixtures are proposed, while preliminary air-flow simulations of the kiln are set and compared against a 1D thermodynamic model of the same system in terms of mean temperatures and mass flows. In the next steps of the project, local combustors results will be employed as input data for the global simulation of kiln air distribution.Reliable overnight industrial LES: challenges and limitations. Application to CSP technologies
http://hdl.handle.net/2117/403705
Reliable overnight industrial LES: challenges and limitations. Application to CSP technologies
Alsalti Baldellou, Àdel; Colomer Rey, Guillem; Hopman, Johannes Arend; Álvarez Farré, Xavier; Gorobets, Andrei; Trias Miquel, Francesc Xavier; Pérez Segarra, Carlos David; Oliva Llena, Asensio
Preserving the operators’ symmetries at the discrete level is crucial to enable reliable DNS and LES simulations of turbulent flows. Moreover, real-world applications demand robust and stable numerical methods suitable for complex geometries. In this regard, this work describes TFA, our novel in-house code, which relies on a symmetry-preserving discretisation for unstructured collocated grids that, apart from being virtually free of artificial dissipation, is shown to be unconditionally stable. To ensure cross-platform portability, the implementation of such a discretisation relies on a minimal set of algebraic kernels. Doing this poses challenges that need to be addressed, like the low arithmetic intensity of the sparse matrix-vector product, the reformulation of boundary conditions and flux limiters, or the efficient computation of eigenbounds to determine the time-step. With the aim of analysing the advantages and disadvantages of this “algebraic” approach, a comparison with OpenFOAM, probably the most widespread open-source CFD code, will be made. Finally, a relevant case from the CSP industry will be presented in order to assess the feasibility of overnight industrial simulations.
Mon, 04 Mar 2024 18:43:57 GMThttp://hdl.handle.net/2117/4037052024-03-04T18:43:57ZAlsalti Baldellou, ÀdelColomer Rey, GuillemHopman, Johannes ArendÁlvarez Farré, XavierGorobets, AndreiTrias Miquel, Francesc XavierPérez Segarra, Carlos DavidOliva Llena, AsensioPreserving the operators’ symmetries at the discrete level is crucial to enable reliable DNS and LES simulations of turbulent flows. Moreover, real-world applications demand robust and stable numerical methods suitable for complex geometries. In this regard, this work describes TFA, our novel in-house code, which relies on a symmetry-preserving discretisation for unstructured collocated grids that, apart from being virtually free of artificial dissipation, is shown to be unconditionally stable. To ensure cross-platform portability, the implementation of such a discretisation relies on a minimal set of algebraic kernels. Doing this poses challenges that need to be addressed, like the low arithmetic intensity of the sparse matrix-vector product, the reformulation of boundary conditions and flux limiters, or the efficient computation of eigenbounds to determine the time-step. With the aim of analysing the advantages and disadvantages of this “algebraic” approach, a comparison with OpenFOAM, probably the most widespread open-source CFD code, will be made. Finally, a relevant case from the CSP industry will be presented in order to assess the feasibility of overnight industrial simulations.