Ramon Peruchi Pacheco da Silva, K. Woodbury, F. Samadi, Joseph Carpenter
An experimental apparatus was constructed to correlate water flow rate and temperature rise under an external band heater. Due to the physical characteristics of the band heater, its transient heating behavior is unknown. This paper investigates the application of Inverse Heat Conduction Problem (IHCP) methods to characterize the heat flux from the band heater. Three experiments with different heating times (5, 10, and 20 seconds) and no flow rate were conducted to measure the transient temperature under the 400 W band heater. Type-T thermocouples measure surface temperature at the centerline of the band heater. The experimental results are computed with five different heat conduction models. The models are chosen to identify how the heat flux response varies from a simplified to a realistic model. Additionally, the results of the experimental heat flux are compared to the manufacturer band heater data (58.9 kW/m2) for each model. The minimum time needed for the heater to fully energize the system is from 10 to 12 seconds. The residuals for each model are analyzed and used to evaluate the appropriateness of the five different models. The results show that the use of simpler models can achieve results similar to those of complex models, with less time and computational cost.
{"title":"Heat Flux Characterization From a Band Heater to Pipe Using Inverse Heat Conduction Problem Method","authors":"Ramon Peruchi Pacheco da Silva, K. Woodbury, F. Samadi, Joseph Carpenter","doi":"10.1115/1.4064731","DOIUrl":"https://doi.org/10.1115/1.4064731","url":null,"abstract":"\u0000 An experimental apparatus was constructed to correlate water flow rate and temperature rise under an external band heater. Due to the physical characteristics of the band heater, its transient heating behavior is unknown. This paper investigates the application of Inverse Heat Conduction Problem (IHCP) methods to characterize the heat flux from the band heater. Three experiments with different heating times (5, 10, and 20 seconds) and no flow rate were conducted to measure the transient temperature under the 400 W band heater. Type-T thermocouples measure surface temperature at the centerline of the band heater. The experimental results are computed with five different heat conduction models. The models are chosen to identify how the heat flux response varies from a simplified to a realistic model. Additionally, the results of the experimental heat flux are compared to the manufacturer band heater data (58.9 kW/m2) for each model. The minimum time needed for the heater to fully energize the system is from 10 to 12 seconds. The residuals for each model are analyzed and used to evaluate the appropriateness of the five different models. The results show that the use of simpler models can achieve results similar to those of complex models, with less time and computational cost.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139841078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large eddy simulation was performed to investigate heat transfer performance of a pulsating flow over teardrop-shaped dimples. A total of six geometries of dimpled surfaces were examined for dimple arrangements of in-line/staggered/original and dimple inclination angle of 0-60 deg. Pulsating flows were generated by sinusoidally varying the volume-averaged velocity. The pulsation frequency and amplitude were changed for the Strouhal number of 0-0.60 and the root-mean-square velocity amplitude normalized by the bulk flow velocity of 0-0.14. The results showed that the surface-averaged Nusselt number and friction factor were larger for the pulsating flow case than those for the steady flow case. The surface-averaged Nusselt number ratio and the friction factor increased with the Strouhal number up to the Strouhal number of 0.30. For the Strouhal number larger than 0.30, they decreased with the Strouhal number or stayed almost constant. Consequently, the heat transfer efficiency index increased with the Strouhal number. The increase in the local Nusselt number ratio due to the flow pulsation was observed at the leading-edge region of the dimples. The results of the streamlines near the dimple showed that the swirling separation bubble was located closer to the leading-edge region due to the pulsation, which resulted in the increase of the absolute values of the turbulent heat flux and the local Nusselt number ratio.
{"title":"Effects of Flow Pulsation and Surface Geometry On Heat Transfer Performance in a Channel with Teardrop-shaped Dimples Investigated by Large Eddy Simulation","authors":"K. Inokuma, Yuki Yawata, A. Murata, K. Iwamoto","doi":"10.1115/1.4064735","DOIUrl":"https://doi.org/10.1115/1.4064735","url":null,"abstract":"\u0000 Large eddy simulation was performed to investigate heat transfer performance of a pulsating flow over teardrop-shaped dimples. A total of six geometries of dimpled surfaces were examined for dimple arrangements of in-line/staggered/original and dimple inclination angle of 0-60 deg. Pulsating flows were generated by sinusoidally varying the volume-averaged velocity. The pulsation frequency and amplitude were changed for the Strouhal number of 0-0.60 and the root-mean-square velocity amplitude normalized by the bulk flow velocity of 0-0.14. The results showed that the surface-averaged Nusselt number and friction factor were larger for the pulsating flow case than those for the steady flow case. The surface-averaged Nusselt number ratio and the friction factor increased with the Strouhal number up to the Strouhal number of 0.30. For the Strouhal number larger than 0.30, they decreased with the Strouhal number or stayed almost constant. Consequently, the heat transfer efficiency index increased with the Strouhal number. The increase in the local Nusselt number ratio due to the flow pulsation was observed at the leading-edge region of the dimples. The results of the streamlines near the dimple showed that the swirling separation bubble was located closer to the leading-edge region due to the pulsation, which resulted in the increase of the absolute values of the turbulent heat flux and the local Nusselt number ratio.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139841468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study proposes the buoyancy and velocity field synergy principle and aims to enhance thermo-hydraulic performance in convective heat transfer. A mechanical energy conservation equation concerning synergy between buoyancy and velocity was derived, which describes the mechanical energy transport and dissipation in convective heat transfer. Two new field synergy numbers, Fsu,g and Fsu,p, were proposed to characterize the degree of synergy between velocity and buoyancy, and the degree of synergy between velocity and pressure gradient over the fluid domain, respectively. The pressure drop of a channel subjected to convective heat transfer is related to not only Gr/Re2 but also Fsu,g. Under a same Gr/Re2, a larger | Fsu,g | leads to a smaller | Fsu,p |, and thus the pressure drop is decreased. Furthermore, the multi-field synergetic relationships among buoyancy, velocity, temperature gradient and pressure gradient were analyzed for convective heat transfer in channels. The correlation between Fsu,p and Fsu,g *Gr/Re2, and the correlation between Fsu,g and a traditional field synergy number characterizing convective heat transfer capability, Fc, were derived, which reveals the coupled mechanisms of mechanical energy dissipation and thermal energy transport. The proposed principle was applied in typical channel flows subjected to convective heat transfer, and its benefits were demonstrated. It is noted that both pressure drop reduction and convective heat transfer enhancement can be achieved in using the proposed principle. This paper provides a new insight for improving thermo-hydraulic performance of heat exchangers.
{"title":"Buoyancy and Velocity Field Synergy Principle in Convective Heat Transfer and its Role in Thermo-Hydraulic Performance Improvement","authors":"Dong Yang, Xinyue Hu, Feilong Chen, Yingli Liu","doi":"10.1115/1.4064734","DOIUrl":"https://doi.org/10.1115/1.4064734","url":null,"abstract":"\u0000 This study proposes the buoyancy and velocity field synergy principle and aims to enhance thermo-hydraulic performance in convective heat transfer. A mechanical energy conservation equation concerning synergy between buoyancy and velocity was derived, which describes the mechanical energy transport and dissipation in convective heat transfer. Two new field synergy numbers, Fsu,g and Fsu,p, were proposed to characterize the degree of synergy between velocity and buoyancy, and the degree of synergy between velocity and pressure gradient over the fluid domain, respectively. The pressure drop of a channel subjected to convective heat transfer is related to not only Gr/Re2 but also Fsu,g. Under a same Gr/Re2, a larger | Fsu,g | leads to a smaller | Fsu,p |, and thus the pressure drop is decreased. Furthermore, the multi-field synergetic relationships among buoyancy, velocity, temperature gradient and pressure gradient were analyzed for convective heat transfer in channels. The correlation between Fsu,p and Fsu,g *Gr/Re2, and the correlation between Fsu,g and a traditional field synergy number characterizing convective heat transfer capability, Fc, were derived, which reveals the coupled mechanisms of mechanical energy dissipation and thermal energy transport. The proposed principle was applied in typical channel flows subjected to convective heat transfer, and its benefits were demonstrated. It is noted that both pressure drop reduction and convective heat transfer enhancement can be achieved in using the proposed principle. This paper provides a new insight for improving thermo-hydraulic performance of heat exchangers.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139841440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present paper, a two-dimensional transient numerical study has been performed to investigate the influence of different fin designs on the melting and heat transfer characteristics of phase change material (PCM) filled inside the square enclosure. Paraffin wax is considered PCM in the present study. Five distinct fin designs were considered: single rectangular, double rectangular, double triangular, double angled, and wire mesh. It is worth noting that all these fin designs have the same heat transfer area. Six parameters were evaluated to determine the best fin configurations: melting time, enhancement ratio (ER), time savings, energy stored, mean power, and Nusselt number. The results show that all the fin designs outperformed as compared to Model 1 (no fin configuration). Among the finned configurations, Model 2 had the poorest performance, taking 1314 seconds to complete melting, while Model 6 had the most efficient fin design, with a melting time reduced by 67.53% compared to Model 1. Model 6 also had the highest ER and mean power, i.e., 70.43% and 199.51%, respectively, and as the melting process continued, the Nusselt number decreased. In addition to the above, we optimized the element size of the wire mesh fin design using the RSM methodology. This optimized design decreased the melting period by 70.04%. Overall, this study provides a comprehensive analysis of different finned configurations for improving the melting performance of PCM in a square enclosure, with the wire-mesh fin design showing the most promising result.
{"title":"Melting and Heat Transfer Characteristics of Phase Change Material: A Comparative Study On Wire Mesh Finned Structure and Other Fin Configurations","authors":"Arun Uniyal, Deepak Kumar, Y. Prajapati","doi":"10.1115/1.4064732","DOIUrl":"https://doi.org/10.1115/1.4064732","url":null,"abstract":"\u0000 In the present paper, a two-dimensional transient numerical study has been performed to investigate the influence of different fin designs on the melting and heat transfer characteristics of phase change material (PCM) filled inside the square enclosure. Paraffin wax is considered PCM in the present study. Five distinct fin designs were considered: single rectangular, double rectangular, double triangular, double angled, and wire mesh. It is worth noting that all these fin designs have the same heat transfer area. Six parameters were evaluated to determine the best fin configurations: melting time, enhancement ratio (ER), time savings, energy stored, mean power, and Nusselt number. The results show that all the fin designs outperformed as compared to Model 1 (no fin configuration). Among the finned configurations, Model 2 had the poorest performance, taking 1314 seconds to complete melting, while Model 6 had the most efficient fin design, with a melting time reduced by 67.53% compared to Model 1. Model 6 also had the highest ER and mean power, i.e., 70.43% and 199.51%, respectively, and as the melting process continued, the Nusselt number decreased. In addition to the above, we optimized the element size of the wire mesh fin design using the RSM methodology. This optimized design decreased the melting period by 70.04%. Overall, this study provides a comprehensive analysis of different finned configurations for improving the melting performance of PCM in a square enclosure, with the wire-mesh fin design showing the most promising result.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139841765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The optimization of heat source layout (HSLO) is able to facilitate superior heat dissipation, thereby addressing the complexities associated with thermal management. However, HSLO is characterized by numerous degrees of freedom and complex interrelations between components. Conventional optimization methodologies often exhibit limitations such as high computational demands and diminished efficiency, particularly with large-scale predicaments. This study introduces the application of deep learning surrogate models grounded in backpropagation neural (BP) networks to optimize heat source layouts. These models afford rapid and precise evaluations, diminishing computational loads and enhancing the efficiency of HSLO. The suggested framework integrates coarse and fine search modules to traverse the layout space and pinpoint optimal configurations competently. Parametric examinations are taken to explore the impact of refinement grades and conductive ratios, which dominates the optimization problem. The pattern changes of the conductive channel have been presented. Moreover, the critical conductive ratio has been found, below which the conductive material can not contribute to heat dissipation. The outcomes elucidate the fundamental processes of HSLO, providing valuable insights for pioneering thermal management strategies.
{"title":"Investigation of Heat Source Layout Optimization by Using Deep Learning Surrogate Models","authors":"Ji Lang, Qianqian Wang, Shan Tong","doi":"10.1115/1.4064733","DOIUrl":"https://doi.org/10.1115/1.4064733","url":null,"abstract":"\u0000 The optimization of heat source layout (HSLO) is able to facilitate superior heat dissipation, thereby addressing the complexities associated with thermal management. However, HSLO is characterized by numerous degrees of freedom and complex interrelations between components. Conventional optimization methodologies often exhibit limitations such as high computational demands and diminished efficiency, particularly with large-scale predicaments. This study introduces the application of deep learning surrogate models grounded in backpropagation neural (BP) networks to optimize heat source layouts. These models afford rapid and precise evaluations, diminishing computational loads and enhancing the efficiency of HSLO. The suggested framework integrates coarse and fine search modules to traverse the layout space and pinpoint optimal configurations competently. Parametric examinations are taken to explore the impact of refinement grades and conductive ratios, which dominates the optimization problem. The pattern changes of the conductive channel have been presented. Moreover, the critical conductive ratio has been found, below which the conductive material can not contribute to heat dissipation. The outcomes elucidate the fundamental processes of HSLO, providing valuable insights for pioneering thermal management strategies.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139840329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present paper, a two-dimensional transient numerical study has been performed to investigate the influence of different fin designs on the melting and heat transfer characteristics of phase change material (PCM) filled inside the square enclosure. Paraffin wax is considered PCM in the present study. Five distinct fin designs were considered: single rectangular, double rectangular, double triangular, double angled, and wire mesh. It is worth noting that all these fin designs have the same heat transfer area. Six parameters were evaluated to determine the best fin configurations: melting time, enhancement ratio (ER), time savings, energy stored, mean power, and Nusselt number. The results show that all the fin designs outperformed as compared to Model 1 (no fin configuration). Among the finned configurations, Model 2 had the poorest performance, taking 1314 seconds to complete melting, while Model 6 had the most efficient fin design, with a melting time reduced by 67.53% compared to Model 1. Model 6 also had the highest ER and mean power, i.e., 70.43% and 199.51%, respectively, and as the melting process continued, the Nusselt number decreased. In addition to the above, we optimized the element size of the wire mesh fin design using the RSM methodology. This optimized design decreased the melting period by 70.04%. Overall, this study provides a comprehensive analysis of different finned configurations for improving the melting performance of PCM in a square enclosure, with the wire-mesh fin design showing the most promising result.
{"title":"Melting and Heat Transfer Characteristics of Phase Change Material: A Comparative Study On Wire Mesh Finned Structure and Other Fin Configurations","authors":"Arun Uniyal, Deepak Kumar, Y. Prajapati","doi":"10.1115/1.4064732","DOIUrl":"https://doi.org/10.1115/1.4064732","url":null,"abstract":"\u0000 In the present paper, a two-dimensional transient numerical study has been performed to investigate the influence of different fin designs on the melting and heat transfer characteristics of phase change material (PCM) filled inside the square enclosure. Paraffin wax is considered PCM in the present study. Five distinct fin designs were considered: single rectangular, double rectangular, double triangular, double angled, and wire mesh. It is worth noting that all these fin designs have the same heat transfer area. Six parameters were evaluated to determine the best fin configurations: melting time, enhancement ratio (ER), time savings, energy stored, mean power, and Nusselt number. The results show that all the fin designs outperformed as compared to Model 1 (no fin configuration). Among the finned configurations, Model 2 had the poorest performance, taking 1314 seconds to complete melting, while Model 6 had the most efficient fin design, with a melting time reduced by 67.53% compared to Model 1. Model 6 also had the highest ER and mean power, i.e., 70.43% and 199.51%, respectively, and as the melting process continued, the Nusselt number decreased. In addition to the above, we optimized the element size of the wire mesh fin design using the RSM methodology. This optimized design decreased the melting period by 70.04%. Overall, this study provides a comprehensive analysis of different finned configurations for improving the melting performance of PCM in a square enclosure, with the wire-mesh fin design showing the most promising result.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139782015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, the linear stability of non-isothermal plane Couette flow (NPCF) in an anisotropic and inhomogeneous porous layer underlying a fluid layer is investigated. The Darcy model is utilized to describe the flow in the porous layer. The stability analysis indicates that the introduction of media-anisotropy (K∧ *) and media-inhomogeneity (in terms of inhomogeneity parameter, A) still renders the isothermal plane Couette flow (IPCF) in such superposed fluid-porous systems unconditionally stable. For NPCF, three different modes: unimodal (porous or fluid mode), bimodal (porous and fluid mode) and trimodal (porous, fluid and porous mode), are observed along the neutral stability curves, and characterized by the secondary flow patterns. It has been found that the instability of the fluid-porous system increases on increasing the media permeability and inhomogeneity along the vertical direction. Contrary to natural convection, at d ∧ = 0.2 (d ∧ = depth of fluid layer/depth of porous layer) and K∧ * = 1, in which the critical wavelength shows both increasing and decreasing characteristic with increasing values of A (0 = A = 5), here in the present study, the same continuously decreases with increasing values of A. Finally, scale analysis indicates that the onset of natural convection requires a relatively higher temperature difference (ΔT) between lower and upper plates in the presence of Couette flow. However, by including media anisotropy and inhomogeneity in the porous media, the system becomes unstable even for a small critical temperature difference of about 2°C.
本文研究了流体层下各向异性非均质多孔层中的非等温平面库尔特流（NPCF）的线性稳定性。采用达西模型来描述多孔层中的流动。稳定性分析表明，引入介质各向异性（K∧*）和介质非均质性（非均质参数 A）仍能使等温平面库尔特流（IPCF）在这种叠加的流体-多孔系统中无条件稳定。对于 NPCF，沿着中性稳定曲线可以观察到三种不同的模式：单模态（多孔或流体模式）、双模态（多孔和流体模式）和三模态（多孔、流体和多孔模式），并以次级流动模式为特征。研究发现，流体-多孔系统的不稳定性随着介质渗透率和垂直方向不均匀性的增加而增加。与自然对流相反，在 d ∧ = 0.2（d ∧ = 流体层深度/多孔层深度）和 K∧ * = 1 时，临界波长随着 A 值（0 = A = 5）的增大而显示出增大和减小的特征，而在本研究中，临界波长同样随着 A 值的增大而持续减小。最后，尺度分析表明，在存在库尔特气流的情况下，自然对流的发生需要下板和上板之间相对较高的温度差（ΔT）。然而，由于多孔介质中存在介质各向异性和不均匀性，即使临界温差很小（约 2°C），系统也会变得不稳定。
{"title":"Non-Isothermal Plane Couette Flow and Its Stability in an Anisotropic and Inhomogeneous Porous Layer Underlying a Fluid Layer Saturated by Water","authors":"Nandita Barman, Anjali Aleria, Premananda Bera","doi":"10.1115/1.4064736","DOIUrl":"https://doi.org/10.1115/1.4064736","url":null,"abstract":"\u0000 In this article, the linear stability of non-isothermal plane Couette flow (NPCF) in an anisotropic and inhomogeneous porous layer underlying a fluid layer is investigated. The Darcy model is utilized to describe the flow in the porous layer. The stability analysis indicates that the introduction of media-anisotropy (K∧ *) and media-inhomogeneity (in terms of inhomogeneity parameter, A) still renders the isothermal plane Couette flow (IPCF) in such superposed fluid-porous systems unconditionally stable. For NPCF, three different modes: unimodal (porous or fluid mode), bimodal (porous and fluid mode) and trimodal (porous, fluid and porous mode), are observed along the neutral stability curves, and characterized by the secondary flow patterns. It has been found that the instability of the fluid-porous system increases on increasing the media permeability and inhomogeneity along the vertical direction. Contrary to natural convection, at d ∧ = 0.2 (d ∧ = depth of fluid layer/depth of porous layer) and K∧ * = 1, in which the critical wavelength shows both increasing and decreasing characteristic with increasing values of A (0 = A = 5), here in the present study, the same continuously decreases with increasing values of A. Finally, scale analysis indicates that the onset of natural convection requires a relatively higher temperature difference (ΔT) between lower and upper plates in the presence of Couette flow. However, by including media anisotropy and inhomogeneity in the porous media, the system becomes unstable even for a small critical temperature difference of about 2°C.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139780869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, the linear stability of non-isothermal plane Couette flow (NPCF) in an anisotropic and inhomogeneous porous layer underlying a fluid layer is investigated. The Darcy model is utilized to describe the flow in the porous layer. The stability analysis indicates that the introduction of media-anisotropy (K∧ *) and media-inhomogeneity (in terms of inhomogeneity parameter, A) still renders the isothermal plane Couette flow (IPCF) in such superposed fluid-porous systems unconditionally stable. For NPCF, three different modes: unimodal (porous or fluid mode), bimodal (porous and fluid mode) and trimodal (porous, fluid and porous mode), are observed along the neutral stability curves, and characterized by the secondary flow patterns. It has been found that the instability of the fluid-porous system increases on increasing the media permeability and inhomogeneity along the vertical direction. Contrary to natural convection, at d ∧ = 0.2 (d ∧ = depth of fluid layer/depth of porous layer) and K∧ * = 1, in which the critical wavelength shows both increasing and decreasing characteristic with increasing values of A (0 = A = 5), here in the present study, the same continuously decreases with increasing values of A. Finally, scale analysis indicates that the onset of natural convection requires a relatively higher temperature difference (ΔT) between lower and upper plates in the presence of Couette flow. However, by including media anisotropy and inhomogeneity in the porous media, the system becomes unstable even for a small critical temperature difference of about 2°C.
本文研究了流体层下各向异性非均质多孔层中的非等温平面库尔特流（NPCF）的线性稳定性。采用达西模型来描述多孔层中的流动。稳定性分析表明，引入介质各向异性（K∧*）和介质非均质性（非均质参数 A）仍能使等温平面库尔特流（IPCF）在这种叠加的流体-多孔系统中无条件稳定。对于 NPCF，沿着中性稳定曲线可以观察到三种不同的模式：单模态（多孔或流体模式）、双模态（多孔和流体模式）和三模态（多孔、流体和多孔模式），并以次级流动模式为特征。研究发现，流体-多孔系统的不稳定性随着介质渗透率和垂直方向不均匀性的增加而增加。与自然对流相反，在 d ∧ = 0.2（d ∧ = 流体层深度/多孔层深度）和 K∧ * = 1 时，临界波长随着 A 值（0 = A = 5）的增大而显示出增大和减小的特征，而在本研究中，临界波长同样随着 A 值的增大而持续减小。最后，尺度分析表明，在存在库尔特气流的情况下，自然对流的发生需要下板和上板之间相对较高的温度差（ΔT）。然而，由于多孔介质中存在介质各向异性和不均匀性，即使临界温差很小（约 2°C），系统也会变得不稳定。
{"title":"Non-Isothermal Plane Couette Flow and Its Stability in an Anisotropic and Inhomogeneous Porous Layer Underlying a Fluid Layer Saturated by Water","authors":"Nandita Barman, Anjali Aleria, Premananda Bera","doi":"10.1115/1.4064736","DOIUrl":"https://doi.org/10.1115/1.4064736","url":null,"abstract":"\u0000 In this article, the linear stability of non-isothermal plane Couette flow (NPCF) in an anisotropic and inhomogeneous porous layer underlying a fluid layer is investigated. The Darcy model is utilized to describe the flow in the porous layer. The stability analysis indicates that the introduction of media-anisotropy (K∧ *) and media-inhomogeneity (in terms of inhomogeneity parameter, A) still renders the isothermal plane Couette flow (IPCF) in such superposed fluid-porous systems unconditionally stable. For NPCF, three different modes: unimodal (porous or fluid mode), bimodal (porous and fluid mode) and trimodal (porous, fluid and porous mode), are observed along the neutral stability curves, and characterized by the secondary flow patterns. It has been found that the instability of the fluid-porous system increases on increasing the media permeability and inhomogeneity along the vertical direction. Contrary to natural convection, at d ∧ = 0.2 (d ∧ = depth of fluid layer/depth of porous layer) and K∧ * = 1, in which the critical wavelength shows both increasing and decreasing characteristic with increasing values of A (0 = A = 5), here in the present study, the same continuously decreases with increasing values of A. Finally, scale analysis indicates that the onset of natural convection requires a relatively higher temperature difference (ΔT) between lower and upper plates in the presence of Couette flow. However, by including media anisotropy and inhomogeneity in the porous media, the system becomes unstable even for a small critical temperature difference of about 2°C.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139840645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The optimization of heat source layout (HSLO) is able to facilitate superior heat dissipation, thereby addressing the complexities associated with thermal management. However, HSLO is characterized by numerous degrees of freedom and complex interrelations between components. Conventional optimization methodologies often exhibit limitations such as high computational demands and diminished efficiency, particularly with large-scale predicaments. This study introduces the application of deep learning surrogate models grounded in backpropagation neural (BP) networks to optimize heat source layouts. These models afford rapid and precise evaluations, diminishing computational loads and enhancing the efficiency of HSLO. The suggested framework integrates coarse and fine search modules to traverse the layout space and pinpoint optimal configurations competently. Parametric examinations are taken to explore the impact of refinement grades and conductive ratios, which dominates the optimization problem. The pattern changes of the conductive channel have been presented. Moreover, the critical conductive ratio has been found, below which the conductive material can not contribute to heat dissipation. The outcomes elucidate the fundamental processes of HSLO, providing valuable insights for pioneering thermal management strategies.
{"title":"Investigation of Heat Source Layout Optimization by Using Deep Learning Surrogate Models","authors":"Ji Lang, Qianqian Wang, Shan Tong","doi":"10.1115/1.4064733","DOIUrl":"https://doi.org/10.1115/1.4064733","url":null,"abstract":"\u0000 The optimization of heat source layout (HSLO) is able to facilitate superior heat dissipation, thereby addressing the complexities associated with thermal management. However, HSLO is characterized by numerous degrees of freedom and complex interrelations between components. Conventional optimization methodologies often exhibit limitations such as high computational demands and diminished efficiency, particularly with large-scale predicaments. This study introduces the application of deep learning surrogate models grounded in backpropagation neural (BP) networks to optimize heat source layouts. These models afford rapid and precise evaluations, diminishing computational loads and enhancing the efficiency of HSLO. The suggested framework integrates coarse and fine search modules to traverse the layout space and pinpoint optimal configurations competently. Parametric examinations are taken to explore the impact of refinement grades and conductive ratios, which dominates the optimization problem. The pattern changes of the conductive channel have been presented. Moreover, the critical conductive ratio has been found, below which the conductive material can not contribute to heat dissipation. The outcomes elucidate the fundamental processes of HSLO, providing valuable insights for pioneering thermal management strategies.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139780588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ramon Peruchi Pacheco da Silva, K. Woodbury, F. Samadi, Joseph Carpenter
An experimental apparatus was constructed to correlate water flow rate and temperature rise under an external band heater. Due to the physical characteristics of the band heater, its transient heating behavior is unknown. This paper investigates the application of Inverse Heat Conduction Problem (IHCP) methods to characterize the heat flux from the band heater. Three experiments with different heating times (5, 10, and 20 seconds) and no flow rate were conducted to measure the transient temperature under the 400 W band heater. Type-T thermocouples measure surface temperature at the centerline of the band heater. The experimental results are computed with five different heat conduction models. The models are chosen to identify how the heat flux response varies from a simplified to a realistic model. Additionally, the results of the experimental heat flux are compared to the manufacturer band heater data (58.9 kW/m2) for each model. The minimum time needed for the heater to fully energize the system is from 10 to 12 seconds. The residuals for each model are analyzed and used to evaluate the appropriateness of the five different models. The results show that the use of simpler models can achieve results similar to those of complex models, with less time and computational cost.
{"title":"Heat Flux Characterization From a Band Heater to Pipe Using Inverse Heat Conduction Problem Method","authors":"Ramon Peruchi Pacheco da Silva, K. Woodbury, F. Samadi, Joseph Carpenter","doi":"10.1115/1.4064731","DOIUrl":"https://doi.org/10.1115/1.4064731","url":null,"abstract":"\u0000 An experimental apparatus was constructed to correlate water flow rate and temperature rise under an external band heater. Due to the physical characteristics of the band heater, its transient heating behavior is unknown. This paper investigates the application of Inverse Heat Conduction Problem (IHCP) methods to characterize the heat flux from the band heater. Three experiments with different heating times (5, 10, and 20 seconds) and no flow rate were conducted to measure the transient temperature under the 400 W band heater. Type-T thermocouples measure surface temperature at the centerline of the band heater. The experimental results are computed with five different heat conduction models. The models are chosen to identify how the heat flux response varies from a simplified to a realistic model. Additionally, the results of the experimental heat flux are compared to the manufacturer band heater data (58.9 kW/m2) for each model. The minimum time needed for the heater to fully energize the system is from 10 to 12 seconds. The residuals for each model are analyzed and used to evaluate the appropriateness of the five different models. The results show that the use of simpler models can achieve results similar to those of complex models, with less time and computational cost.","PeriodicalId":510895,"journal":{"name":"ASME journal of heat and mass transfer","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139781246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：