The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Gian Piero Celata - One of the best experts on this subject based on the ideXlab platform.
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Single-Phase Heat Transfer and Fluid Flow in Micropipes
Heat Transfer Engineering, 2004Co-Authors: Gian Piero CelataAbstract:The objective of this paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime, the friction factor is in good agreement with the Hagen-Poiseuille theory for a Reynolds number below 600–800. For higher values of the Reynolds number, experimental data depart from the Hagen-Poiseuille Law to the side of higher f values. The transition from laminar-to-turbulent flow occurs for Reynolds number in the range 1800–2500. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional (macro) tubes, are not properly adequate for heat transfer rate prediction in microtubes.
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Thermal–hydraulic characteristics of single-phase flow in capillary pipes
Experimental Thermal and Fluid Science, 2003Co-Authors: Gian Piero Celata, Maurizio Cumo, Giuseppe ZummoAbstract:The objective of the present paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime the friction factor is in good agreement with the Hagen–Poiseuille theory for Reynolds number below 600–800. For higher values of Reynolds number, experimental data depart from the Hagen–Poiseuille Law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–2500. Diabatic experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional tubes, are not properly adequate for heat transfer coefficient prediction in microtubes.
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Single-Phase Heat Transfer and Fluid Flow in Micropipes
1st International Conference on Microchannels and Minichannels, 2003Co-Authors: Gian Piero CelataAbstract:The objective of the present paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 600–800. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille Law to the side of higher f values. The transition from laminar-to-turbulent flow occurs for Reynolds number in the range 1800–2500. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional (macro) tubes, are not properly adequate for heat transfer rate prediction in microtubes.Copyright © 2003 by ASME
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Water Single-Phase Fluid Flow and Heat Transfer in Capillary Tubes
Thermal science and engineering, 2003Co-Authors: Alessio Bucci, Gian Piero Celata, Maurizio Cumo, Emanuele Serra, Giuseppe ZummoAbstract:This paper reports the results of an experimental investigation of fluid flow and single-phase heat transfer of water in stainless steel capillary tubes. Three tube diameters are tested: 172 μm, 290 μm and 520 μm, while the Reynolds number varying from 200 up to 6000. Fluid flow experimental results indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 800–1000. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille Law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–3000. This transition is found in good agreement with the well known flow transition for rough commercial tubes. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional size tubes, are not adequate for calculation of heat transfer coefficient in microtubes. In laminar flow the experimental values of heat transfer coefficient are generally higher than those calculated with the classical correlation, while in turbulent flow regime experimental data do not deviate significantly from classical heat transfer correlations. Deviation from classical heat transfer correlations increase as the channel diameter decrease.Copyright © 2003 by ASME
Giuseppe Zummo - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Behaviour and Influence of Channel Wall Roughness and Hydrophobicity in Microchannels
ASME 2nd International Conference on Microchannels and Minichannels, 2004Co-Authors: G.p. Celata, Maurizio Cumo, Stephen J. Mcphail, Giuseppe ZummoAbstract:The sometimes contradictory results available for fluid flow in micropipes show that much is yet to be verified in micro fluid dynamics. In this study the influence of channel wall roughness and of channel wall roughness and of channel wall hydrophobicity on adiabatic flow in circular microchannels is investigated, varying in diameter from 70 μm to 326 μm. The hydrodynamic behaviour of water in smooth tubes down to 30 μm inner diameter (ID) is also ascertained. Within the current experimental accuracy it is found that the classical Hagen-Poiseuille Law for friction factor vs. Reynolds number is respected for all diameters measured and Re > 300. With degassed water, no effect of slip flow conditions due to hydrophobic channel walls even at 70 μm ID was noted, which might suggest that the slip flow phenomenon is associated with local desorption of dissolved gases on the hydrophobic surface, as reported elsewhere in the literature. For roughened glass channels, an increase in friction factor above 64/Re was observed only at the smallest diameter measured, 126 μm. For all experiments, no anticipated transition to turbulent flow was observed (2000 < Retr < 3000).
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Thermal–hydraulic characteristics of single-phase flow in capillary pipes
Experimental Thermal and Fluid Science, 2003Co-Authors: Gian Piero Celata, Maurizio Cumo, Giuseppe ZummoAbstract:The objective of the present paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime the friction factor is in good agreement with the Hagen–Poiseuille theory for Reynolds number below 600–800. For higher values of Reynolds number, experimental data depart from the Hagen–Poiseuille Law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–2500. Diabatic experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional tubes, are not properly adequate for heat transfer coefficient prediction in microtubes.
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Water Single-Phase Fluid Flow and Heat Transfer in Capillary Tubes
Thermal science and engineering, 2003Co-Authors: Alessio Bucci, Gian Piero Celata, Maurizio Cumo, Emanuele Serra, Giuseppe ZummoAbstract:This paper reports the results of an experimental investigation of fluid flow and single-phase heat transfer of water in stainless steel capillary tubes. Three tube diameters are tested: 172 μm, 290 μm and 520 μm, while the Reynolds number varying from 200 up to 6000. Fluid flow experimental results indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 800–1000. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille Law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–3000. This transition is found in good agreement with the well known flow transition for rough commercial tubes. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional size tubes, are not adequate for calculation of heat transfer coefficient in microtubes. In laminar flow the experimental values of heat transfer coefficient are generally higher than those calculated with the classical correlation, while in turbulent flow regime experimental data do not deviate significantly from classical heat transfer correlations. Deviation from classical heat transfer correlations increase as the channel diameter decrease.Copyright © 2003 by ASME
Maurizio Cumo - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Behaviour and Influence of Channel Wall Roughness and Hydrophobicity in Microchannels
ASME 2nd International Conference on Microchannels and Minichannels, 2004Co-Authors: G.p. Celata, Maurizio Cumo, Stephen J. Mcphail, Giuseppe ZummoAbstract:The sometimes contradictory results available for fluid flow in micropipes show that much is yet to be verified in micro fluid dynamics. In this study the influence of channel wall roughness and of channel wall roughness and of channel wall hydrophobicity on adiabatic flow in circular microchannels is investigated, varying in diameter from 70 μm to 326 μm. The hydrodynamic behaviour of water in smooth tubes down to 30 μm inner diameter (ID) is also ascertained. Within the current experimental accuracy it is found that the classical Hagen-Poiseuille Law for friction factor vs. Reynolds number is respected for all diameters measured and Re > 300. With degassed water, no effect of slip flow conditions due to hydrophobic channel walls even at 70 μm ID was noted, which might suggest that the slip flow phenomenon is associated with local desorption of dissolved gases on the hydrophobic surface, as reported elsewhere in the literature. For roughened glass channels, an increase in friction factor above 64/Re was observed only at the smallest diameter measured, 126 μm. For all experiments, no anticipated transition to turbulent flow was observed (2000 < Retr < 3000).
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Thermal–hydraulic characteristics of single-phase flow in capillary pipes
Experimental Thermal and Fluid Science, 2003Co-Authors: Gian Piero Celata, Maurizio Cumo, Giuseppe ZummoAbstract:The objective of the present paper is to provide a general overview of the research carried out so far in single-phase heat transfer and flow in capillary (micro) pipes. Laminar flow and laminar-to-turbulent flow transition are analyzed in detail in order to clarify the discrepancies among the results obtained by different researchers. Experiments performed in the ENEA laboratory indicate that in laminar flow regime the friction factor is in good agreement with the Hagen–Poiseuille theory for Reynolds number below 600–800. For higher values of Reynolds number, experimental data depart from the Hagen–Poiseuille Law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–2500. Diabatic experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional tubes, are not properly adequate for heat transfer coefficient prediction in microtubes.
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Water Single-Phase Fluid Flow and Heat Transfer in Capillary Tubes
Thermal science and engineering, 2003Co-Authors: Alessio Bucci, Gian Piero Celata, Maurizio Cumo, Emanuele Serra, Giuseppe ZummoAbstract:This paper reports the results of an experimental investigation of fluid flow and single-phase heat transfer of water in stainless steel capillary tubes. Three tube diameters are tested: 172 μm, 290 μm and 520 μm, while the Reynolds number varying from 200 up to 6000. Fluid flow experimental results indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 800–1000. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille Law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–3000. This transition is found in good agreement with the well known flow transition for rough commercial tubes. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional size tubes, are not adequate for calculation of heat transfer coefficient in microtubes. In laminar flow the experimental values of heat transfer coefficient are generally higher than those calculated with the classical correlation, while in turbulent flow regime experimental data do not deviate significantly from classical heat transfer correlations. Deviation from classical heat transfer correlations increase as the channel diameter decrease.Copyright © 2003 by ASME
Toru Iijima - One of the best experts on this subject based on the ideXlab platform.
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Water transport phenomena through membranes consisting of vertically-aligned double-walled carbon nanotube array
Carbon, 2017Co-Authors: Hidetoshi Matsumoto, Kenjiro Hata, Motohiro Aiba, Koji Abe, Tomoharu Tokunaga, Shuji Tsuruoka, Yasuhiko Hayashi, Yoshitaka Saito, Shaoling Zhang, Toru IijimaAbstract:Nanofluidics in CNTs is argumentative though it is theoretically calculated by various reports. It is because only a few of experimental reports are available, and the measured permeability is not so large as that suggested from the theoretical calculations. Also, water motion suppression in the confined space has not been exhibited by flux measurement. The present work explores these yet-unsolved discrepancies using the measurable size membrane of vertically aligned double-walled carbon nanotube array, which is borne with durability and flexibility, and a conventional measurement method is applied to the membranes. Water motion suppression occurs in the CNT confined space significantly, depending on temperature. Additionally, it is confirmed that the obtained permeability correlates to the reported experimental results with regard to the relationship between CNT length and permeability, and the correlation does not agree with permeability calculated from the Hagen-Poiseuille Law. These results pose an insight into the inherent water transport characteristics in the CNT confined space.
Steven Jansen - One of the best experts on this subject based on the ideXlab platform.
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The application of various anatomical techniques for studying the hydraulic network in tomato fruit pedicels
Protoplasma, 2010Co-Authors: Dragana Rančić, Sofija Pekić Quarrie, Radenko Radošević, Maja Terzić, Ilinka Pećinar, Radmila Stikić, Steven JansenAbstract:The abscission zone in fruit pedicels plays an important role in affecting not only water uptake in the developing fruit, but also in the transport of chemical signals from root to shoot. In order to characterize the hydraulic network of tomato fruit pedicels, we applied various techniques, including light, fluorescence microscopy, electron microscopy, maceration, tissue clearing, and X-ray computed tomography. Because of significant changes in xylem anatomy, the abscission zone in tomato fruit pedicels is illustrated to show a clear reduction in hydraulic conductance. Based on anatomical measurements, the theoretical axial xylem conductance was calculated via the Hagen–Poiseuille Law, suggesting that the hydraulic resistance of the abscission zone increases at least two orders of magnitude compared to the pedicel zone near the stem. The advantages and shortcomings of the microscope techniques applied are discussed.
