The Experts below are selected from a list of 13233 Experts worldwide ranked by ideXlab platform
Yun Wook Hwang - One of the best experts on this subject based on the ideXlab platform.
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heat transfer and pressure drop characteristics during the in tube cooling process of carbon dioxide in the supercritical region
International Journal of Refrigeration-revue Internationale Du Froid, 2003Co-Authors: Seok Ho Yoon, Yun Wook HwangAbstract:Abstract This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tubes in which carbon dioxide flows are made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg m−2 s−1 by a variable speed Gear Pump, and the inlet pressures are adjusted from 7.5 to 8.8 MPa. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by Blasius' equation. Using the measured data, a new empirical correlation to predict the near-critical heat transfer coefficient has been developed. Most of the experimental data can be predicted by the new correlation within a relative deviation of ±20%.
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heat transfer and pressure drop characteristics during the in tube cooling process of carbon dioxide in the supercritical region
International Journal of Refrigeration-revue Internationale Du Froid, 2003Co-Authors: Seok Ho Yoon, Yun Wook HwangAbstract:This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tubes in which carbon dioxide flows are made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg m � 2 s � 1 by a variable speed Gear Pump, and the inlet pressures are adjusted from 7.5 to 8.8 MPa. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by Blasius’ equation. Using the measured data, a new empirical correlation to predict the near-critical heat transfer coefficient has been developed. Most of the experimental data can be predicted by the new correlation within a relative deviation of � 20%. # 2003 Elsevier Ltd and IIR. All rights reserved.
P J Gamezmontero - One of the best experts on this subject based on the ideXlab platform.
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three dimensional numerical simulation of an external Gear Pump with decompression slot and meshing contact point
Journal of Fluids Engineering-transactions of The Asme, 2015Co-Authors: R Castilla, P J Gamezmontero, D Del Campo, G Raush, M Garciavilchez, Esteve CodinaAbstract:Recently several works have been published on numerical simulation of an external Gear Pump (EGP). Such kinds of Pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the Gearing mechanism between Gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal-metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a LINUX cluster with a solver developed with the OPENFOAM Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the Gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.
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experimental analysis of the flow dynamics in the suction chamber of an external Gear Pump
International Journal of Mechanical Sciences, 2011Co-Authors: N Erturk, A Verne, R Castilla, P J Gamezmontero, J A FerreAbstract:Time-Resolved Particle Image Velocimetry (TRPIV) has been used to investigate the flow inside the suction chamber of an external Gear Pump where the movement of the fluid through the Pump is maintained by the rotation of the Gears. The main purpose of this paper is to study the characteristics of the complex flow pattern of this Pump system in order to help in improving its total performance. The applied experimental techniques establish a method that allows visualising the flow inside the Gear Pump with a high rotational velocity system. Small micro air bubbles have been used as flow seeding. The images have been processed using domestic PIV software that uses specific aspects of the TRPIV technique. Instantaneous and phase-locked ensemble average fluid motions have been obtained for different Gear Pump rotational velocities to investigate the turbulence effect of rotating Gears to the system.
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analysis of the turbulence in the suction chamber of an external Gear Pump using time resolved particle image velocimetry
Flow Measurement and Instrumentation, 2008Co-Authors: R Castilla, A Verne, P J Gamezmontero, J Wojciechowski, E CodinaAbstract:Abstract The use of air bubbles for the analysis of the turbulence in the suction chamber of a Gear Pump with Time Resolved Particle Image Velocimetry (TRPIV) is considered. It is the first time, as far as the authors know, that the flow inside a Gear Pump is observed with a non-intrusive technique. Although there are drawbacks of using air bubbles as flow tracers, it is the only option available in this case, since solid particles and water drops could drastically damage the steel-made Gears. It is shown that if the bubbles are small enough (around 100 μm), the buoyancy is not a significant problem for the typical velocities involved in the experiments. On the other hand, if the number of particles per interrogation area is between 10 and 20, as is normally suggested in the literature, the modification of the speed of sound and, hence, the danger of having a compressible flow, is also negligible. Using air bubbles as tracers for the TRPIV, the turbulence for three experiments, at different diameter-based Reynolds numbers, is analysed. The time series of the velocity at different distances to the Gearing zone of the Gear Pump are considered, as well as the wavenumber distribution of the density of energy, calculated from the vorticity field. The results show that for high enough Reynolds number the integral timescale of the turbulence, obtained from the autocorrelation function, is approximately the same as the Gearing period. Also, the spectral distribution in frequency show an energy transport to large scale, as well as the spectral distribution in wavenumber. This latter shows also an stepper range related to the enstrophy cascade towards the small scales. That suggests the two-dimensionality of the turbulence created in the suction chamber.
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contact problems of a trochoidal Gear Pump
International Journal of Mechanical Sciences, 2006Co-Authors: P J Gamezmontero, R Castilla, M Khamashta, Esteve CodinaAbstract:The aim of the approach of this paper is to characterise contact stress of a trochoidal-Gear set when it works as part of the hydraulic machine. It is important to know that the contact stress forces in a trochoidal-type machine is important because the machine cannot be adjusted for wear. The main difficulty in calculating the contact forces is to determine the forces that are transmitted through each contact point. Since there are many points of contact, at any instant, the problem is statically indeterminate. The first part of this paper presents a simplified analytical model of a trochoidal-type machine when friction at the contact points is neglected. From this study, the performance of the Gear set is evaluated through the calculation of the normal maximum contact stress in the Gear teeth. Then the second part of the paper presents a finite element model of the same machine. The analysis of both models is for quasi-static conditions. An experimental approach using a prototype model of the Gear set provides the maximum contact stress on a pair of teeth through photoelasticity measurement techniques of the same machine. The results from the two models and the experimental work are compared and important conclusions are drawn and discussed.
R Castilla - One of the best experts on this subject based on the ideXlab platform.
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three dimensional numerical simulation of an external Gear Pump with decompression slot and meshing contact point
Journal of Fluids Engineering-transactions of The Asme, 2015Co-Authors: R Castilla, P J Gamezmontero, D Del Campo, G Raush, M Garciavilchez, Esteve CodinaAbstract:Recently several works have been published on numerical simulation of an external Gear Pump (EGP). Such kinds of Pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the Gearing mechanism between Gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal-metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a LINUX cluster with a solver developed with the OPENFOAM Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the Gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.
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experimental analysis of the flow dynamics in the suction chamber of an external Gear Pump
International Journal of Mechanical Sciences, 2011Co-Authors: N Erturk, A Verne, R Castilla, P J Gamezmontero, J A FerreAbstract:Time-Resolved Particle Image Velocimetry (TRPIV) has been used to investigate the flow inside the suction chamber of an external Gear Pump where the movement of the fluid through the Pump is maintained by the rotation of the Gears. The main purpose of this paper is to study the characteristics of the complex flow pattern of this Pump system in order to help in improving its total performance. The applied experimental techniques establish a method that allows visualising the flow inside the Gear Pump with a high rotational velocity system. Small micro air bubbles have been used as flow seeding. The images have been processed using domestic PIV software that uses specific aspects of the TRPIV technique. Instantaneous and phase-locked ensemble average fluid motions have been obtained for different Gear Pump rotational velocities to investigate the turbulence effect of rotating Gears to the system.
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analysis of the turbulence in the suction chamber of an external Gear Pump using time resolved particle image velocimetry
Flow Measurement and Instrumentation, 2008Co-Authors: R Castilla, A Verne, P J Gamezmontero, J Wojciechowski, E CodinaAbstract:Abstract The use of air bubbles for the analysis of the turbulence in the suction chamber of a Gear Pump with Time Resolved Particle Image Velocimetry (TRPIV) is considered. It is the first time, as far as the authors know, that the flow inside a Gear Pump is observed with a non-intrusive technique. Although there are drawbacks of using air bubbles as flow tracers, it is the only option available in this case, since solid particles and water drops could drastically damage the steel-made Gears. It is shown that if the bubbles are small enough (around 100 μm), the buoyancy is not a significant problem for the typical velocities involved in the experiments. On the other hand, if the number of particles per interrogation area is between 10 and 20, as is normally suggested in the literature, the modification of the speed of sound and, hence, the danger of having a compressible flow, is also negligible. Using air bubbles as tracers for the TRPIV, the turbulence for three experiments, at different diameter-based Reynolds numbers, is analysed. The time series of the velocity at different distances to the Gearing zone of the Gear Pump are considered, as well as the wavenumber distribution of the density of energy, calculated from the vorticity field. The results show that for high enough Reynolds number the integral timescale of the turbulence, obtained from the autocorrelation function, is approximately the same as the Gearing period. Also, the spectral distribution in frequency show an energy transport to large scale, as well as the spectral distribution in wavenumber. This latter shows also an stepper range related to the enstrophy cascade towards the small scales. That suggests the two-dimensionality of the turbulence created in the suction chamber.
-
contact problems of a trochoidal Gear Pump
International Journal of Mechanical Sciences, 2006Co-Authors: P J Gamezmontero, R Castilla, M Khamashta, Esteve CodinaAbstract:The aim of the approach of this paper is to characterise contact stress of a trochoidal-Gear set when it works as part of the hydraulic machine. It is important to know that the contact stress forces in a trochoidal-type machine is important because the machine cannot be adjusted for wear. The main difficulty in calculating the contact forces is to determine the forces that are transmitted through each contact point. Since there are many points of contact, at any instant, the problem is statically indeterminate. The first part of this paper presents a simplified analytical model of a trochoidal-type machine when friction at the contact points is neglected. From this study, the performance of the Gear set is evaluated through the calculation of the normal maximum contact stress in the Gear teeth. Then the second part of the paper presents a finite element model of the same machine. The analysis of both models is for quasi-static conditions. An experimental approach using a prototype model of the Gear set provides the maximum contact stress on a pair of teeth through photoelasticity measurement techniques of the same machine. The results from the two models and the experimental work are compared and important conclusions are drawn and discussed.
Seok Ho Yoon - One of the best experts on this subject based on the ideXlab platform.
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heat transfer and pressure drop characteristics during the in tube cooling process of carbon dioxide in the supercritical region
International Journal of Refrigeration-revue Internationale Du Froid, 2003Co-Authors: Seok Ho Yoon, Yun Wook HwangAbstract:Abstract This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tubes in which carbon dioxide flows are made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg m−2 s−1 by a variable speed Gear Pump, and the inlet pressures are adjusted from 7.5 to 8.8 MPa. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by Blasius' equation. Using the measured data, a new empirical correlation to predict the near-critical heat transfer coefficient has been developed. Most of the experimental data can be predicted by the new correlation within a relative deviation of ±20%.
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heat transfer and pressure drop characteristics during the in tube cooling process of carbon dioxide in the supercritical region
International Journal of Refrigeration-revue Internationale Du Froid, 2003Co-Authors: Seok Ho Yoon, Yun Wook HwangAbstract:This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tubes in which carbon dioxide flows are made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg m � 2 s � 1 by a variable speed Gear Pump, and the inlet pressures are adjusted from 7.5 to 8.8 MPa. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by Blasius’ equation. Using the measured data, a new empirical correlation to predict the near-critical heat transfer coefficient has been developed. Most of the experimental data can be predicted by the new correlation within a relative deviation of � 20%. # 2003 Elsevier Ltd and IIR. All rights reserved.
J A Ferre - One of the best experts on this subject based on the ideXlab platform.
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experimental analysis of the flow dynamics in the suction chamber of an external Gear Pump
International Journal of Mechanical Sciences, 2011Co-Authors: N Erturk, A Verne, R Castilla, P J Gamezmontero, J A FerreAbstract:Time-Resolved Particle Image Velocimetry (TRPIV) has been used to investigate the flow inside the suction chamber of an external Gear Pump where the movement of the fluid through the Pump is maintained by the rotation of the Gears. The main purpose of this paper is to study the characteristics of the complex flow pattern of this Pump system in order to help in improving its total performance. The applied experimental techniques establish a method that allows visualising the flow inside the Gear Pump with a high rotational velocity system. Small micro air bubbles have been used as flow seeding. The images have been processed using domestic PIV software that uses specific aspects of the TRPIV technique. Instantaneous and phase-locked ensemble average fluid motions have been obtained for different Gear Pump rotational velocities to investigate the turbulence effect of rotating Gears to the system.
