Melting and resolidification of a mixture of two metal powders with significantly different melting points under irradiation of a stationary or a moving Gaussian laser beam were investigated numerically and experimentally. The liquid motion driven by capillary and gravity forces as well as the shrinkage of the powder bed caused by the overall density change were taken into account in the physical model. The liquid flow was formulated by using Darcy’s law, and the energy equation was given using a temperature transforming model. Predictions were compared with experimental results obtained with nickel braze and AISI 1018 steel powder. The effects of laser properties and the scanning velocity on the laser sintering process were also investigated. An empirical correlation that can be used to predict the of cross sectional area of the heat affected zone is proposed.
{"title":"3-D Sintering of Two-Component Metal Powders With Stationary and Moving Laser Beams","authors":"Yuwen Zhang, A. Faghri, C. W. Buckley, T. Bergman","doi":"10.1115/imece1999-1079","DOIUrl":"https://doi.org/10.1115/imece1999-1079","url":null,"abstract":"\u0000 Melting and resolidification of a mixture of two metal powders with significantly different melting points under irradiation of a stationary or a moving Gaussian laser beam were investigated numerically and experimentally. The liquid motion driven by capillary and gravity forces as well as the shrinkage of the powder bed caused by the overall density change were taken into account in the physical model. The liquid flow was formulated by using Darcy’s law, and the energy equation was given using a temperature transforming model. Predictions were compared with experimental results obtained with nickel braze and AISI 1018 steel powder. The effects of laser properties and the scanning velocity on the laser sintering process were also investigated. An empirical correlation that can be used to predict the of cross sectional area of the heat affected zone is proposed.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127071133","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}
Extended micron-scale structures were produced in thermoplastic melts from initially large clusters of conducting carbon black particles transported by three-dimensional chaotic mixing. The structures formed networks that were captured by solidification and rendered the composite materials electrically conducting. A systematic study was carried out to assess the influence of key parameters and relate the electrical properties to the microstructures. Micrographs showed complex structures exhibiting patterns characteristic of chaos. Electrical measurements indicated that conductivity was achieved at carbon black concentrations significantly lower than achievable by common mixing methods, and lower than reported recently for two-dimensional chaotic mixing.
{"title":"Particle Transport via Three-Dimensional Chaotic Advection to Produce Electrically Conducting Plastics With Powder Additives","authors":"R. Danescu, D. Zumbrunnen","doi":"10.1115/imece1999-1072","DOIUrl":"https://doi.org/10.1115/imece1999-1072","url":null,"abstract":"\u0000 Extended micron-scale structures were produced in thermoplastic melts from initially large clusters of conducting carbon black particles transported by three-dimensional chaotic mixing. The structures formed networks that were captured by solidification and rendered the composite materials electrically conducting. A systematic study was carried out to assess the influence of key parameters and relate the electrical properties to the microstructures. Micrographs showed complex structures exhibiting patterns characteristic of chaos. Electrical measurements indicated that conductivity was achieved at carbon black concentrations significantly lower than achievable by common mixing methods, and lower than reported recently for two-dimensional chaotic mixing.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126785054","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}
J. Sheu, M. Giridharan, S. Hong, R. Shekarriz, C. Call
The main objective of this study is to develop an efficient meso-scale thermo-catalytic air purification system for battlefield applications. In this system, heated air is passed through a catalytic reactor to destroy toxic materials. The main constraints in designing this system are size, weight and fuel/power consumption. A successful design of this type of purification system depends to a large extent on the efficiency and performance of the heat exchanger. As a first step, a heat exchanger system that consists of several units of planar counter flow heat exchangers stacked on top of each other has been designed and fabricated. A CFD (Computational Fluid Dynamics) model has been used to understand the flow and heat transfer characteristics as well as to predict the effectiveness of the heat exchanger. A series of experiments have been performed to collect data to validate the CFD results. It will be shown that the data for temperature and effectiveness are in agreement with CFD predictions. Parametric simulations have also been performed to evaluate the heat exchanger performance as functions of geometric and operating conditions. The results indicate that axial conduction in the exchanger plate and the thermal boundary layer film resistance are the limiting factors in the heat exchanger performance.
{"title":"Computational and Experimental Analysis of a Meso-Scale Heat Exchanger","authors":"J. Sheu, M. Giridharan, S. Hong, R. Shekarriz, C. Call","doi":"10.1115/imece1999-1067","DOIUrl":"https://doi.org/10.1115/imece1999-1067","url":null,"abstract":"\u0000 The main objective of this study is to develop an efficient meso-scale thermo-catalytic air purification system for battlefield applications. In this system, heated air is passed through a catalytic reactor to destroy toxic materials. The main constraints in designing this system are size, weight and fuel/power consumption. A successful design of this type of purification system depends to a large extent on the efficiency and performance of the heat exchanger. As a first step, a heat exchanger system that consists of several units of planar counter flow heat exchangers stacked on top of each other has been designed and fabricated. A CFD (Computational Fluid Dynamics) model has been used to understand the flow and heat transfer characteristics as well as to predict the effectiveness of the heat exchanger. A series of experiments have been performed to collect data to validate the CFD results. It will be shown that the data for temperature and effectiveness are in agreement with CFD predictions. Parametric simulations have also been performed to evaluate the heat exchanger performance as functions of geometric and operating conditions. The results indicate that axial conduction in the exchanger plate and the thermal boundary layer film resistance are the limiting factors in the heat exchanger performance.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133461536","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}
At present most work treats radiative transport in heterogeneous media as if it were a homogeneous medium, then relies on different methods to simulate the medium heterogeneity or uses similar governing equations with assigned distributions for coefficients. This approach is widely used although almost never found in other fields of heat and mass transport. The lack of generality in present theoretical treatments of radiative transport in heterogeneous media is addressed by rigorous development of a set of governing equations. The new rigorous equations for radiation transport in heterogeneous media are presented for the first time. As part of the development of the new set of equations for electromagnetic and spectral intensity fields, the diffusion approximation is explored.
{"title":"Radiation Heat Transport in Porous Media","authors":"V. Travkin, I. Catton","doi":"10.1115/imece1999-1060","DOIUrl":"https://doi.org/10.1115/imece1999-1060","url":null,"abstract":"\u0000 At present most work treats radiative transport in heterogeneous media as if it were a homogeneous medium, then relies on different methods to simulate the medium heterogeneity or uses similar governing equations with assigned distributions for coefficients. This approach is widely used although almost never found in other fields of heat and mass transport. The lack of generality in present theoretical treatments of radiative transport in heterogeneous media is addressed by rigorous development of a set of governing equations. The new rigorous equations for radiation transport in heterogeneous media are presented for the first time. As part of the development of the new set of equations for electromagnetic and spectral intensity fields, the diffusion approximation is explored.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122422395","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}
Drying of coated paper is a complex process that includes the three mechanisms of heat transfer (conduction, convection, and radiation) coupled with water (liquid, vapor and bound), air, and binder mass transfer. Limited work has been conducted so far to mathematically simulate this drying process. This paper critically reviews the major relevant theoretical models and discusses each model’s strengths and shortcomings. The critical review reveals that there is a need for a better and more complete model to capture all the physics of the process of drying of coated paper. Furthermore, the theoretical results (e.g. drying rates, heat and mass transfer fluxes, temperature and species’ concentration profiles) should be directly verified against laboratory and machine data under various operating conditions.
{"title":"A Critical Review of Drying Models for Coated Paper","authors":"H. Noboa, J. Seyed-Yagoobi","doi":"10.1115/imece1999-1082","DOIUrl":"https://doi.org/10.1115/imece1999-1082","url":null,"abstract":"\u0000 Drying of coated paper is a complex process that includes the three mechanisms of heat transfer (conduction, convection, and radiation) coupled with water (liquid, vapor and bound), air, and binder mass transfer. Limited work has been conducted so far to mathematically simulate this drying process. This paper critically reviews the major relevant theoretical models and discusses each model’s strengths and shortcomings. The critical review reveals that there is a need for a better and more complete model to capture all the physics of the process of drying of coated paper. Furthermore, the theoretical results (e.g. drying rates, heat and mass transfer fluxes, temperature and species’ concentration profiles) should be directly verified against laboratory and machine data under various operating conditions.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"117 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115251637","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}
N. Ashraf, H. Carter, K. Casey, L. Chow, S. Corban, M. K. Drost, A. Gumm, Z. Hao, A. Hasan, J. Kapat, L. Kramer, M. Newton, K. Sundaram, J. Vaidya, C. Wong, K. Yerkes
The preliminary design and analysis of a meso-scale refrigerator is presented here. The device is to be designed out of layers of silicon wafers bonded together and is to be fabricated through the techniques of microelectronics. The intended application of the device is an integrated heat removal system for electronics or photonic chips or modules. The paper presents a functional decomposition of the entire system, thermodynamic feasibility analysis, alternative configurations for two of the functions: actuation and compression, and parametric analysis for two alternative candidates for compressor actuation. A set of reasonable design requirements is first formulated. Overall function of the devices is decomposed into nine major sub-functions. Comparison of different alternatives for compression and actuation suggests that electrostatic actuation integrated with centrifugal compression is a viable option. Two different ways to implement electrostatic actuation are considered in details: variable capacitance motor and electrostatic induction motor. A set of design relations and criteria needed to obtain the optimal design of each motor is presented along with a discussion on relative effects of the main design parameters.
{"title":"Design and Analysis of a Meso-Scale Refrigerator","authors":"N. Ashraf, H. Carter, K. Casey, L. Chow, S. Corban, M. K. Drost, A. Gumm, Z. Hao, A. Hasan, J. Kapat, L. Kramer, M. Newton, K. Sundaram, J. Vaidya, C. Wong, K. Yerkes","doi":"10.1115/imece1999-1068","DOIUrl":"https://doi.org/10.1115/imece1999-1068","url":null,"abstract":"\u0000 The preliminary design and analysis of a meso-scale refrigerator is presented here. The device is to be designed out of layers of silicon wafers bonded together and is to be fabricated through the techniques of microelectronics. The intended application of the device is an integrated heat removal system for electronics or photonic chips or modules. The paper presents a functional decomposition of the entire system, thermodynamic feasibility analysis, alternative configurations for two of the functions: actuation and compression, and parametric analysis for two alternative candidates for compressor actuation.\u0000 A set of reasonable design requirements is first formulated. Overall function of the devices is decomposed into nine major sub-functions. Comparison of different alternatives for compression and actuation suggests that electrostatic actuation integrated with centrifugal compression is a viable option. Two different ways to implement electrostatic actuation are considered in details: variable capacitance motor and electrostatic induction motor. A set of design relations and criteria needed to obtain the optimal design of each motor is presented along with a discussion on relative effects of the main design parameters.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132457412","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}
A 3-D thermal model for resistance spot welding in aluminum is presented. The numerical model, validated with experimental findings, considers phase change and the associated weld-pool convection. A parametric study is performed to determine the influence of welding features such as faying surface (work-piece contact surface) contact resistance, current, electrode-work-piece surface-thermal-contact-conductance and electrode tip diameter. These parameters have significant effects on the nugget and heat-affected-zone geometry. The phase change morphology, including melting and solidification rates and weld pool dynamics, is also significantly influenced by the parameters studied. The strongest convection was observed at the center of the molten pool in a plane aligned with gravity. Although two prominent convection cells develop, the phase change morphology is not significantly affected due to the short welding time (less than 0.05 seconds) and low fluid velocity (smaller than 1 × 10−2 mm/s). The nugget grows nonlinearly with increasing current and faying surface contact resistance while diminishing with increasing electrode work-piece surface-thermal-contact-conductance. The influence of faying surface contact resistance on nugget size is less than that of the other parameters. Optimum selection of electrode tip diameter provides the best possible nugget. The duration of weld pool existence increases with the increasing current but decreases with the increasing electrode work-piece surface-thermal-contact-conductance.
{"title":"Three-Dimensional Thermal Model of Resistance Spot Welding in Aluminum","authors":"A. Kabir, J. Khan, K. Broach","doi":"10.1115/imece1999-1094","DOIUrl":"https://doi.org/10.1115/imece1999-1094","url":null,"abstract":"\u0000 A 3-D thermal model for resistance spot welding in aluminum is presented. The numerical model, validated with experimental findings, considers phase change and the associated weld-pool convection. A parametric study is performed to determine the influence of welding features such as faying surface (work-piece contact surface) contact resistance, current, electrode-work-piece surface-thermal-contact-conductance and electrode tip diameter. These parameters have significant effects on the nugget and heat-affected-zone geometry. The phase change morphology, including melting and solidification rates and weld pool dynamics, is also significantly influenced by the parameters studied. The strongest convection was observed at the center of the molten pool in a plane aligned with gravity. Although two prominent convection cells develop, the phase change morphology is not significantly affected due to the short welding time (less than 0.05 seconds) and low fluid velocity (smaller than 1 × 10−2 mm/s). The nugget grows nonlinearly with increasing current and faying surface contact resistance while diminishing with increasing electrode work-piece surface-thermal-contact-conductance. The influence of faying surface contact resistance on nugget size is less than that of the other parameters. Optimum selection of electrode tip diameter provides the best possible nugget. The duration of weld pool existence increases with the increasing current but decreases with the increasing electrode work-piece surface-thermal-contact-conductance.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124540042","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}
Research on turbulent mixing processes is of great interest to those working on turbulent-reactive flows. In this paper, a detailed study has been performed for the evolution of scalar fields of different initial integral scales in decaying, homogeneous and isotropic turbulence using DNS technique. Passive scalar mixing in a cubical decaying, homogeneous, isotropic turbulence field is considered. The three-dimensional incompressible Navier-Stokes equations together with scalar equation are solved using Fractional Step Method. The convective and diffusive terms in governing equations are discretised by Compact Finite Difference Scheme. The 32 × 32 × 32 uniform staggered grids are used. The present simulation is performed at Taylor Reynolds number of 28.83. In this paper, the evolution of scalar RMS and scalar dissipation rate for different integral length scales has been presented. The initial velocity vector and Probability Density Function (PDF) of scalar at different eddy turn over time have also been presented.
{"title":"Direct Numerical Simulation of Mixing of a Passive in Decaying Turbulence","authors":"P. Deb, P. Majumdar","doi":"10.1115/imece1999-1086","DOIUrl":"https://doi.org/10.1115/imece1999-1086","url":null,"abstract":"\u0000 Research on turbulent mixing processes is of great interest to those working on turbulent-reactive flows. In this paper, a detailed study has been performed for the evolution of scalar fields of different initial integral scales in decaying, homogeneous and isotropic turbulence using DNS technique. Passive scalar mixing in a cubical decaying, homogeneous, isotropic turbulence field is considered. The three-dimensional incompressible Navier-Stokes equations together with scalar equation are solved using Fractional Step Method. The convective and diffusive terms in governing equations are discretised by Compact Finite Difference Scheme. The 32 × 32 × 32 uniform staggered grids are used. The present simulation is performed at Taylor Reynolds number of 28.83. In this paper, the evolution of scalar RMS and scalar dissipation rate for different integral length scales has been presented. The initial velocity vector and Probability Density Function (PDF) of scalar at different eddy turn over time have also been presented.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115299907","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 radiative behavior of the glass as it flows through a continuous glass furnace is studied by applying the Discrete Ordinates Method (DOM). Through the application of the DOM the radiant intensity is calculated at each of the control volumes inside the glass tank domain. Consequently, the heat fluxes of the emitted and irradiated energy in the glass are obtained. The results are presented in terms of the radiant heat fluxes distribution and temperature profile of the glass. In addition, the variation of the glass surface emissivity is studied in order to provide further understanding of the impact of this property in the glass overall thermal behavior.
{"title":"Application of the Discrete Ordinates Method to a Continuous Glass Furnace Model","authors":"S. C. Rodicio, K. S. Chapman","doi":"10.1115/imece1999-1088","DOIUrl":"https://doi.org/10.1115/imece1999-1088","url":null,"abstract":"\u0000 The radiative behavior of the glass as it flows through a continuous glass furnace is studied by applying the Discrete Ordinates Method (DOM). Through the application of the DOM the radiant intensity is calculated at each of the control volumes inside the glass tank domain. Consequently, the heat fluxes of the emitted and irradiated energy in the glass are obtained. The results are presented in terms of the radiant heat fluxes distribution and temperature profile of the glass. In addition, the variation of the glass surface emissivity is studied in order to provide further understanding of the impact of this property in the glass overall thermal behavior.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117162290","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 common architecture of the fluid delivery devices employed in the horizontal processing of printed wiring boards, makes use of high velocity jets directed normally or at some angle towards the board which moves above rollers. Usually, a single slot jet or a linear arrays of jets are employed in order to increase the transport properties of the flow in the vicinity of the printed wiring board. In the present study, a geometry resembling a fluid delivery device used in printed wiring board manufacturing was investigated both experimentally and numerically. The printed wiring board is represented by an endless belt, which is transported horizontally by a system of rollers. The working fluid is delivered by an array of 13 square jets with a hydraulic diameter of 5.02 mm and a separation distance between jets of 4 hydraulic diameters. Two confinement plates located on each side of the jet array are used to confine the flow region and adjust the flow resistance at the two openings — between the rollers and the confinement plates — symmetrically located with respect to the centerline of the row of jets. The experimental setup and the numerical model both allowed the investigation of the effect of complex confinement (due to the board, confinement plates and rollers) and of the moving boundaries (impingement surface and rollers) on the characteristics of impinging flow. The flow field and the heat transfer characteristics were investigated for the jet Reynolds number ranging from 500 to 2000, non-dimensional impingement surface velocity ranging from 0 to 1 and non-dimensional impingement distance of 3 and 5. The CFD simulations were performed using the commercial CFD code PHOENICS. Flow visualization and particle image velocimetry were employed in order to experimentally investigate the flow field and validate the CFD simulations. The predicted results compare well with the observed jet behavior. A detailed description of the flow physics is presented. The numerical simulations show that for the same mass flow rate, the row of jets has a higher transport effectiveness when compared to a slot jet.
{"title":"Transport Processes for a Row of Confined Jets Impinging on a Moving Surface","authors":"C. Dinu, D. E. Beasley","doi":"10.1115/imece1999-1084","DOIUrl":"https://doi.org/10.1115/imece1999-1084","url":null,"abstract":"\u0000 The common architecture of the fluid delivery devices employed in the horizontal processing of printed wiring boards, makes use of high velocity jets directed normally or at some angle towards the board which moves above rollers. Usually, a single slot jet or a linear arrays of jets are employed in order to increase the transport properties of the flow in the vicinity of the printed wiring board. In the present study, a geometry resembling a fluid delivery device used in printed wiring board manufacturing was investigated both experimentally and numerically. The printed wiring board is represented by an endless belt, which is transported horizontally by a system of rollers. The working fluid is delivered by an array of 13 square jets with a hydraulic diameter of 5.02 mm and a separation distance between jets of 4 hydraulic diameters. Two confinement plates located on each side of the jet array are used to confine the flow region and adjust the flow resistance at the two openings — between the rollers and the confinement plates — symmetrically located with respect to the centerline of the row of jets. The experimental setup and the numerical model both allowed the investigation of the effect of complex confinement (due to the board, confinement plates and rollers) and of the moving boundaries (impingement surface and rollers) on the characteristics of impinging flow. The flow field and the heat transfer characteristics were investigated for the jet Reynolds number ranging from 500 to 2000, non-dimensional impingement surface velocity ranging from 0 to 1 and non-dimensional impingement distance of 3 and 5. The CFD simulations were performed using the commercial CFD code PHOENICS. Flow visualization and particle image velocimetry were employed in order to experimentally investigate the flow field and validate the CFD simulations. The predicted results compare well with the observed jet behavior. A detailed description of the flow physics is presented. The numerical simulations show that for the same mass flow rate, the row of jets has a higher transport effectiveness when compared to a slot jet.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129706497","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}
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