The Experts below are selected from a list of 23961 Experts worldwide ranked by ideXlab platform
Atilla Bayram - One of the best experts on this subject based on the ideXlab platform.
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Equivalent Roughness Height for Plane Bed Under Oscillatory Flow
Estuarine Coastal and Shelf Science, 2009Co-Authors: Benoît Camenen, Magnus Larson, Atilla BayramAbstract:A new relationship between the Roughness height and the main hydrodynamic and sediment parameters for plane beds under oscillatory conditions is presented. In order to derive such a relationship, a large data base encompassing plane-bed experiments was compiled from previous investigations and analyzed. Different methods to estimate the Roughness height were investigated. Comparisons between the data and different existing predictive formulas for the bed Roughness obtained from the literature were also performed. A relationship involving the grain size and Shields parameter only, which is commonly proposed, appeared to be insufficient to characterize the Roughness. The Roughness height was also found to be a function of the sediment density and the settling velocity. A critical Shields parameter was identified up to which the effective Roughness Ratio is proportional to the Shields parameter only. The new empirical equation developed in this study provides the highest predictive skill for all conditions investigated.
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Equivalent Roughness Height for Plane Bed under Steady Flow
Journal of Hydraulic Engineering, 2006Co-Authors: Benoît Camenen, Atilla Bayram, Magnus LarsonAbstract:This paper presents a new relationship between the Roughness height and the main hydrodynamic and sediment parameters for plane beds under steady current conditions. In order to derive such a formula, a large data base involving plane-bed experiments was compiled from previous investigations and analyzed. Comparisons between the data and different existing predictive formulas for the bed Roughness obtained from the literature were also made. A relationship with the Shields parameter only, which is commonly proposed, appeared to be insufficient. The Roughness was also found to be a function of a Froude number and a dimensionless settling velocity. A critical Shields parameter was identified up to which the equivalent Roughness Ratio is proportional to the Shields parameter. The new empirical equation that was developed yields the best results for all conditions investigated, and should improve the understanding of the total shear stress.
Hyun Sun Park - One of the best experts on this subject based on the ideXlab platform.
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Boiling heat transfer and critical heat flux evaluation of the pool boiling on micro structured surface
'Elsevier BV', 2018Co-Authors: Sh Kim, Kiyofumi Moriyama, Kim Moo Hwan, Gc Lee, Jy Kang, Hyun Sun ParkAbstract:We study the effectiveness of microstructured surfaces in enhancing the boiling heat transfer (BHT) and critical heat flux (CHF). A set of experiments is designed with thirteen prepared samples: twelve with a microstructured surface, and one with a bare surface. The samples are fabricated using microelectrome-chanical systems (MEMS) techniques. The samples are tested using pool boiling experiments in saturated and atmospheric pressure conditions. The experimental results show that BHT increases with the surface Roughness, defined as the Ratio of the rough surface area to the projected area, but this enhancement gradually slows. The heat transfer coefficient of the structured surface is more than 300% that of the bare surface. The increase in the heating surface area due to the Roughness Ratio improves nucleate BHT due to the enhancement of convective heat transfer. The structured surface shows a 350% improvement in CHF over the bare surface. However, through analysis of the capillary flow rate on the structured surface, a critical gap size that limits the CHF is found. The critical gap size is discussed analytically and compared with experimental data. Designs for optimal boiling performance are proposed by studying the role of microstructured surfaces in both BHT and CHF. (C) 2015 Elsevier Ltd. All rights reserved.1352
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heat flux partitioning analysis of pool boiling on micro structured surface using infrared visualization
International Journal of Heat and Mass Transfer, 2016Co-Authors: Seol Ha Kim, Jun Young Kang, Kiyofumi Moriyama, Hyun Sun Park, Gi Cheol Lee, Moo Hwan KimAbstract:Abstract We study a heat flux partitioning analysis of nucleate pool boiling on microstructured surface through infrared visualization technique. A heat flux partitioning analysis of the nucleate pool boiling consists of three kinds of heat flux mechanisms; convective, quenching and evaporative heat flux. It is importance of understanding the dominance among those heat flux mechanisms to fundamental study of the nucleate boiling heat transfer, but it is not clearly figured out. In this study, directly measuring the boiling parameters; bubble departure size, bubble releasing frequency, nucleation site density and bubble growth time through the infrared visualization technique, a nucleate boiling heat flux portioning analysis on pool boiling has been carried out. The experimental results indicate that sum of the three heat flux partitions from the measured boiling parameters shows good agreement with the experimentally given total heat flux. In addition, the quenching heat flux and evaporative heat flux becomes dominant at high heat flux regime by numerous bubble geneRation and fast bubble growth. On the microstructured surface, the increased heating surface area by the Roughness Ratio intactly contributes the heat transfer performance enhancement, and the area increase effect have to be reflected on the heat flux partitioning calculation. Although there are still many arguments of the heat flux portioning model analysis on pool boiling heat transfer from literatures and the methodological limitation due to the chaotic boiling phenomena, this study gives good inspiRation and understanding of the boiling heat transfer mechanism and the importance of each heat transfer mechanism.
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boiling heat transfer and critical heat flux evaluation of the pool boiling on micro structured surface
International Journal of Heat and Mass Transfer, 2015Co-Authors: Jun Young Kang, Kiyofumi Moriyama, Hyun Sun ParkAbstract:Abstract We study the effectiveness of microstructured surfaces in enhancing the boiling heat transfer (BHT) and critical heat flux (CHF). A set of experiments is designed with thirteen prepared samples: twelve with a microstructured surface, and one with a bare surface. The samples are fabricated using microelectromechanical systems (MEMS) techniques. The samples are tested using pool boiling experiments in saturated and atmospheric pressure conditions. The experimental results show that BHT increases with the surface Roughness, defined as the Ratio of the rough surface area to the projected area, but this enhancement gradually slows. The heat transfer coefficient of the structured surface is more than 300% that of the bare surface. The increase in the heating surface area due to the Roughness Ratio improves nucleate BHT due to the enhancement of convective heat transfer. The structured surface shows a 350% improvement in CHF over the bare surface. However, through analysis of the capillary flow rate on the structured surface, a critical gap size that limits the CHF is found. The critical gap size is discussed analytically and compared with experimental data. Designs for optimal boiling performance are proposed by studying the role of microstructured surfaces in both BHT and CHF.
Benoît Camenen - One of the best experts on this subject based on the ideXlab platform.
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Equivalent Roughness Height for Plane Bed Under Oscillatory Flow
Estuarine Coastal and Shelf Science, 2009Co-Authors: Benoît Camenen, Magnus Larson, Atilla BayramAbstract:A new relationship between the Roughness height and the main hydrodynamic and sediment parameters for plane beds under oscillatory conditions is presented. In order to derive such a relationship, a large data base encompassing plane-bed experiments was compiled from previous investigations and analyzed. Different methods to estimate the Roughness height were investigated. Comparisons between the data and different existing predictive formulas for the bed Roughness obtained from the literature were also performed. A relationship involving the grain size and Shields parameter only, which is commonly proposed, appeared to be insufficient to characterize the Roughness. The Roughness height was also found to be a function of the sediment density and the settling velocity. A critical Shields parameter was identified up to which the effective Roughness Ratio is proportional to the Shields parameter only. The new empirical equation developed in this study provides the highest predictive skill for all conditions investigated.
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Equivalent Roughness Height for Plane Bed under Steady Flow
Journal of Hydraulic Engineering, 2006Co-Authors: Benoît Camenen, Atilla Bayram, Magnus LarsonAbstract:This paper presents a new relationship between the Roughness height and the main hydrodynamic and sediment parameters for plane beds under steady current conditions. In order to derive such a formula, a large data base involving plane-bed experiments was compiled from previous investigations and analyzed. Comparisons between the data and different existing predictive formulas for the bed Roughness obtained from the literature were also made. A relationship with the Shields parameter only, which is commonly proposed, appeared to be insufficient. The Roughness was also found to be a function of a Froude number and a dimensionless settling velocity. A critical Shields parameter was identified up to which the equivalent Roughness Ratio is proportional to the Shields parameter. The new empirical equation that was developed yields the best results for all conditions investigated, and should improve the understanding of the total shear stress.
Magnus Larson - One of the best experts on this subject based on the ideXlab platform.
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Equivalent Roughness Height for Plane Bed Under Oscillatory Flow
Estuarine Coastal and Shelf Science, 2009Co-Authors: Benoît Camenen, Magnus Larson, Atilla BayramAbstract:A new relationship between the Roughness height and the main hydrodynamic and sediment parameters for plane beds under oscillatory conditions is presented. In order to derive such a relationship, a large data base encompassing plane-bed experiments was compiled from previous investigations and analyzed. Different methods to estimate the Roughness height were investigated. Comparisons between the data and different existing predictive formulas for the bed Roughness obtained from the literature were also performed. A relationship involving the grain size and Shields parameter only, which is commonly proposed, appeared to be insufficient to characterize the Roughness. The Roughness height was also found to be a function of the sediment density and the settling velocity. A critical Shields parameter was identified up to which the effective Roughness Ratio is proportional to the Shields parameter only. The new empirical equation developed in this study provides the highest predictive skill for all conditions investigated.
-
Equivalent Roughness Height for Plane Bed under Steady Flow
Journal of Hydraulic Engineering, 2006Co-Authors: Benoît Camenen, Atilla Bayram, Magnus LarsonAbstract:This paper presents a new relationship between the Roughness height and the main hydrodynamic and sediment parameters for plane beds under steady current conditions. In order to derive such a formula, a large data base involving plane-bed experiments was compiled from previous investigations and analyzed. Comparisons between the data and different existing predictive formulas for the bed Roughness obtained from the literature were also made. A relationship with the Shields parameter only, which is commonly proposed, appeared to be insufficient. The Roughness was also found to be a function of a Froude number and a dimensionless settling velocity. A critical Shields parameter was identified up to which the equivalent Roughness Ratio is proportional to the Shields parameter. The new empirical equation that was developed yields the best results for all conditions investigated, and should improve the understanding of the total shear stress.
Kiyofumi Moriyama - One of the best experts on this subject based on the ideXlab platform.
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Boiling heat transfer and critical heat flux evaluation of the pool boiling on micro structured surface
'Elsevier BV', 2018Co-Authors: Sh Kim, Kiyofumi Moriyama, Kim Moo Hwan, Gc Lee, Jy Kang, Hyun Sun ParkAbstract:We study the effectiveness of microstructured surfaces in enhancing the boiling heat transfer (BHT) and critical heat flux (CHF). A set of experiments is designed with thirteen prepared samples: twelve with a microstructured surface, and one with a bare surface. The samples are fabricated using microelectrome-chanical systems (MEMS) techniques. The samples are tested using pool boiling experiments in saturated and atmospheric pressure conditions. The experimental results show that BHT increases with the surface Roughness, defined as the Ratio of the rough surface area to the projected area, but this enhancement gradually slows. The heat transfer coefficient of the structured surface is more than 300% that of the bare surface. The increase in the heating surface area due to the Roughness Ratio improves nucleate BHT due to the enhancement of convective heat transfer. The structured surface shows a 350% improvement in CHF over the bare surface. However, through analysis of the capillary flow rate on the structured surface, a critical gap size that limits the CHF is found. The critical gap size is discussed analytically and compared with experimental data. Designs for optimal boiling performance are proposed by studying the role of microstructured surfaces in both BHT and CHF. (C) 2015 Elsevier Ltd. All rights reserved.1352
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heat flux partitioning analysis of pool boiling on micro structured surface using infrared visualization
International Journal of Heat and Mass Transfer, 2016Co-Authors: Seol Ha Kim, Jun Young Kang, Kiyofumi Moriyama, Hyun Sun Park, Gi Cheol Lee, Moo Hwan KimAbstract:Abstract We study a heat flux partitioning analysis of nucleate pool boiling on microstructured surface through infrared visualization technique. A heat flux partitioning analysis of the nucleate pool boiling consists of three kinds of heat flux mechanisms; convective, quenching and evaporative heat flux. It is importance of understanding the dominance among those heat flux mechanisms to fundamental study of the nucleate boiling heat transfer, but it is not clearly figured out. In this study, directly measuring the boiling parameters; bubble departure size, bubble releasing frequency, nucleation site density and bubble growth time through the infrared visualization technique, a nucleate boiling heat flux portioning analysis on pool boiling has been carried out. The experimental results indicate that sum of the three heat flux partitions from the measured boiling parameters shows good agreement with the experimentally given total heat flux. In addition, the quenching heat flux and evaporative heat flux becomes dominant at high heat flux regime by numerous bubble geneRation and fast bubble growth. On the microstructured surface, the increased heating surface area by the Roughness Ratio intactly contributes the heat transfer performance enhancement, and the area increase effect have to be reflected on the heat flux partitioning calculation. Although there are still many arguments of the heat flux portioning model analysis on pool boiling heat transfer from literatures and the methodological limitation due to the chaotic boiling phenomena, this study gives good inspiRation and understanding of the boiling heat transfer mechanism and the importance of each heat transfer mechanism.
-
boiling heat transfer and critical heat flux evaluation of the pool boiling on micro structured surface
International Journal of Heat and Mass Transfer, 2015Co-Authors: Jun Young Kang, Kiyofumi Moriyama, Hyun Sun ParkAbstract:Abstract We study the effectiveness of microstructured surfaces in enhancing the boiling heat transfer (BHT) and critical heat flux (CHF). A set of experiments is designed with thirteen prepared samples: twelve with a microstructured surface, and one with a bare surface. The samples are fabricated using microelectromechanical systems (MEMS) techniques. The samples are tested using pool boiling experiments in saturated and atmospheric pressure conditions. The experimental results show that BHT increases with the surface Roughness, defined as the Ratio of the rough surface area to the projected area, but this enhancement gradually slows. The heat transfer coefficient of the structured surface is more than 300% that of the bare surface. The increase in the heating surface area due to the Roughness Ratio improves nucleate BHT due to the enhancement of convective heat transfer. The structured surface shows a 350% improvement in CHF over the bare surface. However, through analysis of the capillary flow rate on the structured surface, a critical gap size that limits the CHF is found. The critical gap size is discussed analytically and compared with experimental data. Designs for optimal boiling performance are proposed by studying the role of microstructured surfaces in both BHT and CHF.
