Dépouillements

Modeling of ceramic particle heating and melting in a microwave plasma / Kaushik Saha in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031002/1-10] Titre : Modeling of ceramic particle heating and melting in a microwave plasma Type de document : texte imprimé Auteurs : Kaushik Saha, Auteur ; Swetaprovo Chaudhuri, Auteur ; Baki M. Cetegen, Auteur Année de publication : 2011 Article en page(s) : pp. [031002/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microwave  plasma  Ceramic  particles  Heat-up  Melting Index. décimale : 536 Chaleur. Thermodynamique Résumé : A comprehensive model based on finite volume method was developed to analyze the heat-up and the melting of ceramic particles injected into a microwave excited laminar air plasma flow field. Plasma flow field was simulated as a hot gas flow generated by volumetric heat addition in the microwave coupling region, resulting in a temperature of 6000 K. Alumina and zirconia particles of different diameters were injected into the axisymmetric laminar plasma flow at different injection velocities and locations. Additionally, noncontinuum effects, variation of transport properties of plasma surrounding the spherical particles and absorption of microwave radiation in the ceramic particles were considered in the model. Model predictions suggest that zirconia and alumina particles with diameters less than 50 µm can be effectively melted in a microwave plasma and can produce more uniform melt states. Microwave plasma environment with the ability to inject particles into the plasma core provide the opportunity to create more uniform melt states as compared with dc arc plasmas that are influenced by characteristic arc root fluctuations and turbulent dispersions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Modeling of ceramic particle heating and melting in a microwave plasma [texte imprimé] / Kaushik Saha, Auteur ; Swetaprovo Chaudhuri, Auteur ; Baki M. Cetegen, Auteur . - 2011 . - pp. [031002/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031002/1-10] Mots-clés : Microwave  plasma  Ceramic  particles  Heat-up  Melting Index. décimale : 536 Chaleur. Thermodynamique Résumé : A comprehensive model based on finite volume method was developed to analyze the heat-up and the melting of ceramic particles injected into a microwave excited laminar air plasma flow field. Plasma flow field was simulated as a hot gas flow generated by volumetric heat addition in the microwave coupling region, resulting in a temperature of 6000 K. Alumina and zirconia particles of different diameters were injected into the axisymmetric laminar plasma flow at different injection velocities and locations. Additionally, noncontinuum effects, variation of transport properties of plasma surrounding the spherical particles and absorption of microwave radiation in the ceramic particles were considered in the model. Model predictions suggest that zirconia and alumina particles with diameters less than 50 µm can be effectively melted in a microwave plasma and can produce more uniform melt states. Microwave plasma environment with the ability to inject particles into the plasma core provide the opportunity to create more uniform melt states as compared with dc arc plasmas that are influenced by characteristic arc root fluctuations and turbulent dispersions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Modeling of ultrafast phase change processes in a thin metal film irradiated by femtosecond laser pulse trains / Jing Huang in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031003/1-8] Titre : Modeling of ultrafast phase change processes in a thin metal film irradiated by femtosecond laser pulse trains Type de document : texte imprimé Auteurs : Jing Huang, Auteur ; Yuwen Zhang, Auteur ; J. K. Chen, Auteur Année de publication : 2011 Article en page(s) : pp. [031003/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Gold  Laser  beam  effects  Melting  Metallic  thin  films  Phase  change  materials  Solidification  Vaporisation Index. décimale : 536 Chaleur. Thermodynamique Résumé : Ultrashort laser pulses can be generated in the form of a pulse train. In this paper, the ultrafast phase change processes of a 1 µm free-standing gold film irradiated by femtosecond laser pulse trains are simulated numerically. A two-temperature model coupled with interface tracking method is developed to describe the ultrafast melting, vaporization, and resolidification processes. To deal with the large span in time scale, variable time steps are adopted. A laser pulse train consists of several pulse bursts with a repetition rate of 0.5–1 MHz. Each pulse burst contains 3–10 pulses with an interval of 50 ps–10 ns. The simulation results show that with such configuration, to achieve the same melting depth, the maximum temperature in the film decreases significantly in comparison to that of a single pulse. Although the total energy depositing on the film will be lifted, more energy will be transferred into the deeper part, instead of accumulating in the subsurface layer. This leads to lower temperature and temperature gradient, which is favorable in laser sintering and laser machining. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Modeling of ultrafast phase change processes in a thin metal film irradiated by femtosecond laser pulse trains [texte imprimé] / Jing Huang, Auteur ; Yuwen Zhang, Auteur ; J. K. Chen, Auteur . - 2011 . - pp. [031003/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031003/1-8] Mots-clés : Gold  Laser  beam  effects  Melting  Metallic  thin  films  Phase  change  materials  Solidification  Vaporisation Index. décimale : 536 Chaleur. Thermodynamique Résumé : Ultrashort laser pulses can be generated in the form of a pulse train. In this paper, the ultrafast phase change processes of a 1 µm free-standing gold film irradiated by femtosecond laser pulse trains are simulated numerically. A two-temperature model coupled with interface tracking method is developed to describe the ultrafast melting, vaporization, and resolidification processes. To deal with the large span in time scale, variable time steps are adopted. A laser pulse train consists of several pulse bursts with a repetition rate of 0.5–1 MHz. Each pulse burst contains 3–10 pulses with an interval of 50 ps–10 ns. The simulation results show that with such configuration, to achieve the same melting depth, the maximum temperature in the film decreases significantly in comparison to that of a single pulse. Although the total energy depositing on the film will be lifted, more energy will be transferred into the deeper part, instead of accumulating in the subsurface layer. This leads to lower temperature and temperature gradient, which is favorable in laser sintering and laser machining. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Characteristics of pool boiling bubble dynamics in bead packed porous structures / Calvin H. Li in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031004/1-10] Titre : Characteristics of pool boiling bubble dynamics in bead packed porous structures Type de document : texte imprimé Auteurs : Calvin H. Li, Auteur ; Ting Li, Auteur ; Paul Hodgins, Auteur Année de publication : 2011 Article en page(s) : pp. [031004/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Two-phase  heat  transfer  Porous  structure  Bubble  dynamics  Critical  heat  flux Index. décimale : 536 Chaleur. Thermodynamique Résumé : Spherical glass and copper beads have been used to create bead packed porous structures for an investigation of two-phase heat transfer bubble dynamics under geometric constraints. The results demonstrated a variety of bubble dynamics characteristics under a range of heating conditions. The bubble generation, growth, and detachment during the nucleate pool boiling heat transfer have been filmed, the heating surface temperatures and heat flux were recorded, and theoretical models have been employed to study bubble dynamic characteristics. Computer simulation results were combined with experimental observations to clarify the details of the vapor bubble growth process and the liquid water replenishing the inside of the porous structures. This investigation has clearly shown, with both experimental and computer simulation evidence, that the millimeter scale bead packed porous structures could greatly influence pool boiling heat transfer by forcing a single bubble to depart at a smaller size, as compared with that in a plain surface situation at low heat flux situations, and could trigger the earlier occurrence of critical heat flux by trapping the vapor into interstitial space and forming a vapor column net at high heat flux situations. The results also proved data for further development of theoretical models of pool boiling heat transfer in bead packed porous structures. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Characteristics of pool boiling bubble dynamics in bead packed porous structures [texte imprimé] / Calvin H. Li, Auteur ; Ting Li, Auteur ; Paul Hodgins, Auteur . - 2011 . - pp. [031004/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031004/1-10] Mots-clés : Two-phase  heat  transfer  Porous  structure  Bubble  dynamics  Critical  heat  flux Index. décimale : 536 Chaleur. Thermodynamique Résumé : Spherical glass and copper beads have been used to create bead packed porous structures for an investigation of two-phase heat transfer bubble dynamics under geometric constraints. The results demonstrated a variety of bubble dynamics characteristics under a range of heating conditions. The bubble generation, growth, and detachment during the nucleate pool boiling heat transfer have been filmed, the heating surface temperatures and heat flux were recorded, and theoretical models have been employed to study bubble dynamic characteristics. Computer simulation results were combined with experimental observations to clarify the details of the vapor bubble growth process and the liquid water replenishing the inside of the porous structures. This investigation has clearly shown, with both experimental and computer simulation evidence, that the millimeter scale bead packed porous structures could greatly influence pool boiling heat transfer by forcing a single bubble to depart at a smaller size, as compared with that in a plain surface situation at low heat flux situations, and could trigger the earlier occurrence of critical heat flux by trapping the vapor into interstitial space and forming a vapor column net at high heat flux situations. The results also proved data for further development of theoretical models of pool boiling heat transfer in bead packed porous structures. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Thermal science of weld bead defects / P. S. Wei in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031005/1-22] Titre : Thermal science of weld bead defects : a review Type de document : texte imprimé Auteurs : P. S. Wei, Auteur Année de publication : 2011 Article en page(s) : pp. [031005/1-22] Note générale : Physique Langues : Anglais (eng) Mots-clés : Weld  defects  Bead  defects  Surface  patterns  Pattern  selection  Humping  Rippling Index. décimale : 536 Chaleur. Thermodynamique Résumé : Mechanisms for the formation of bead defects, such as humping, gouging, rippling, and other unexpected surface patterns, encountered in welding or drilling are interpreted and reviewed from thermal-fluid science viewpoint. These defects usually accompanying with porosity, undercut, segregation, stress concentration, etc., seriously reduce the properties and strength of the joint or solidification. Even though different mechanisms for formation of the defects have been extensively proposed in the past, more systematical understanding of pattern formations from thermal, fluid, physics, electromagnetic, pattern selections, and metallurgy sciences is still limited. The effects of working parameters and properties on humping and rippling, for example, can be systematically and quantitatively interpreted from scale analysis presented in this work. Good comparison with experimental results reveals mechanisms of different surface patterns. The mechanistic findings for bead defects are also useful for other manufacturing and materials processing. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Thermal science of weld bead defects : a review [texte imprimé] / P. S. Wei, Auteur . - 2011 . - pp. [031005/1-22]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031005/1-22] Mots-clés : Weld  defects  Bead  defects  Surface  patterns  Pattern  selection  Humping  Rippling Index. décimale : 536 Chaleur. Thermodynamique Résumé : Mechanisms for the formation of bead defects, such as humping, gouging, rippling, and other unexpected surface patterns, encountered in welding or drilling are interpreted and reviewed from thermal-fluid science viewpoint. These defects usually accompanying with porosity, undercut, segregation, stress concentration, etc., seriously reduce the properties and strength of the joint or solidification. Even though different mechanisms for formation of the defects have been extensively proposed in the past, more systematical understanding of pattern formations from thermal, fluid, physics, electromagnetic, pattern selections, and metallurgy sciences is still limited. The effects of working parameters and properties on humping and rippling, for example, can be systematically and quantitatively interpreted from scale analysis presented in this work. Good comparison with experimental results reveals mechanisms of different surface patterns. The mechanistic findings for bead defects are also useful for other manufacturing and materials processing. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

The experimental and theoretical evaluation of an indirect cooling system for machining / Jay C. Rozzi in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031006/1-10] Titre : The experimental and theoretical evaluation of an indirect cooling system for machining Type de document : texte imprimé Auteurs : Jay C. Rozzi, Auteur ; John K. Sanders, Auteur ; Weibo Chen, Auteur Année de publication : 2011 Article en page(s) : pp. [031006/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  transfer  Two-phase  Cryogenic  Machining  Microchannel Index. décimale : 536 Chaleur. Thermodynamique Résumé : Cutting fluids have been used in machining processes for many years to decrease the temperature during machining by spraying the coolant into the machining zone directly on the cutting tool and the part. This has the effect of decreasing the tool temperature, which increases tool life and improves the part quality. These benefits come with significant drawbacks. Cutting fluids are environmentally unfriendly, costly, and potentially toxic. An alternative that has been evaluated in this paper is an internal cooling system (ICS) for lathe turning, which cools the cutting tool using a very small amount of an inert, cryogenic working fluid routed through a microchannel heat exchanger (MHX) that is mounted beneath the cutting tool insert. The working fluid absorbs the heat generated during the machining process after which it is harmlessly vented to the environment. This indirect cooling technique results in an environmentally friendly machining process that uses no cutting fluids, enables increased processing speed, and reduces manufacturing costs. An approximate heat transfer model was developed and used to predict the tool life as a function of the tool cooling approach for various speeds. Machining experiments were completed to validate the heat transfer model and confirm that the ICS can significantly improve tool life relative to conventional flood cooling. The validated model was then used to evaluate alternative cooling approaches using the ICS. It was found that the use of a cryogenic working fluid can significantly improve tool life at all cutting speeds but that the latent heat capacity of the working fluid should exceed the expected maximum heat transfer rate into the tool. This work established that the ICS approach is an effective means to increase tool life without the disadvantages associated with external cryogenic cooling methods. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] The experimental and theoretical evaluation of an indirect cooling system for machining [texte imprimé] / Jay C. Rozzi, Auteur ; John K. Sanders, Auteur ; Weibo Chen, Auteur . - 2011 . - pp. [031006/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031006/1-10] Mots-clés : Heat  transfer  Two-phase  Cryogenic  Machining  Microchannel Index. décimale : 536 Chaleur. Thermodynamique Résumé : Cutting fluids have been used in machining processes for many years to decrease the temperature during machining by spraying the coolant into the machining zone directly on the cutting tool and the part. This has the effect of decreasing the tool temperature, which increases tool life and improves the part quality. These benefits come with significant drawbacks. Cutting fluids are environmentally unfriendly, costly, and potentially toxic. An alternative that has been evaluated in this paper is an internal cooling system (ICS) for lathe turning, which cools the cutting tool using a very small amount of an inert, cryogenic working fluid routed through a microchannel heat exchanger (MHX) that is mounted beneath the cutting tool insert. The working fluid absorbs the heat generated during the machining process after which it is harmlessly vented to the environment. This indirect cooling technique results in an environmentally friendly machining process that uses no cutting fluids, enables increased processing speed, and reduces manufacturing costs. An approximate heat transfer model was developed and used to predict the tool life as a function of the tool cooling approach for various speeds. Machining experiments were completed to validate the heat transfer model and confirm that the ICS can significantly improve tool life relative to conventional flood cooling. The validated model was then used to evaluate alternative cooling approaches using the ICS. It was found that the use of a cryogenic working fluid can significantly improve tool life at all cutting speeds but that the latent heat capacity of the working fluid should exceed the expected maximum heat transfer rate into the tool. This work established that the ICS approach is an effective means to increase tool life without the disadvantages associated with external cryogenic cooling methods. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Modeling of the off-axis high power diode laser cladding process / Shaoyi Wen in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031007/1-10] Titre : Modeling of the off-axis high power diode laser cladding process Type de document : texte imprimé Auteurs : Shaoyi Wen, Auteur ; Shin, Yung C., Auteur Année de publication : 2011 Article en page(s) : pp. [031007/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : HPDL  Laser  cladding  Level  set  Track  geometry Index. décimale : 536 Chaleur. Thermodynamique Résumé : Off-axis high power diode laser (HPDL) cladding is commonly used for surface quality enhancement such as coating, part repairing, etc. Although some laser cladding models are available in literature, little has been reported on the modeling of powder flow and molten pool for a rectangular beam with side powder injection. In this article, a custom-designed flat nozzle delivers the powder material into a distinct molten pool formed by a HPDL with a rectangular beam. A powder model is first presented to reveal the powder flow behavior below the flat nozzle. Key parameters such as nozzle inclination angle, rectangular beam profile, shielding gas flow rates, and powder feed rate are incorporated so that spatial powder density, powder velocity, and temperature distribution are distinctly investigated. Then in order to describe thermal and fluidic behaviors around the molten pool formed by the rectangular beam, a three-dimensional self-consistent cladding model is developed with the incorporation of the distributed powder properties as input. The level set method is adopted to track the complex free surface evolution. Temperature fields and fluid motion in the molten pool area resulting from the profile of rectangular beam are distinctly revealed. The effect of continuous mass addition is also embedded into the governing equations, making the model more accurate. A HPDL cladding with little dilution is formed and the simulated results agree well with the experiment. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Modeling of the off-axis high power diode laser cladding process [texte imprimé] / Shaoyi Wen, Auteur ; Shin, Yung C., Auteur . - 2011 . - pp. [031007/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031007/1-10] Mots-clés : HPDL  Laser  cladding  Level  set  Track  geometry Index. décimale : 536 Chaleur. Thermodynamique Résumé : Off-axis high power diode laser (HPDL) cladding is commonly used for surface quality enhancement such as coating, part repairing, etc. Although some laser cladding models are available in literature, little has been reported on the modeling of powder flow and molten pool for a rectangular beam with side powder injection. In this article, a custom-designed flat nozzle delivers the powder material into a distinct molten pool formed by a HPDL with a rectangular beam. A powder model is first presented to reveal the powder flow behavior below the flat nozzle. Key parameters such as nozzle inclination angle, rectangular beam profile, shielding gas flow rates, and powder feed rate are incorporated so that spatial powder density, powder velocity, and temperature distribution are distinctly investigated. Then in order to describe thermal and fluidic behaviors around the molten pool formed by the rectangular beam, a three-dimensional self-consistent cladding model is developed with the incorporation of the distributed powder properties as input. The level set method is adopted to track the complex free surface evolution. Temperature fields and fluid motion in the molten pool area resulting from the profile of rectangular beam are distinctly revealed. The effect of continuous mass addition is also embedded into the governing equations, making the model more accurate. A HPDL cladding with little dilution is formed and the simulated results agree well with the experiment. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Theoretical Analysis of Microwave Heating of dielectric materials filled in a rectangular waveguide with various resonator distances / Phadungsak Rattanadecho in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031008/1-10] Titre : Theoretical Analysis of Microwave Heating of dielectric materials filled in a rectangular waveguide with various resonator distances Type de document : texte imprimé Auteurs : Phadungsak Rattanadecho, Auteur ; Waraporn Klinbun, Auteur Année de publication : 2011 Article en page(s) : pp. [031008/1-10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microwave  heating  Rectangular  waveguide  TE10  mode  Porous  medium  Resonator Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper proposes mathematical models of the microwave heating process of dielectric materials filled in a rectangular waveguide with a resonator. A microwave system supplies a monochromatic wave in a fundamental mode (TE10 mode). A convection exchange at the upper surface of the sample is considered. The effects of resonator distance and operating frequency on distributions of electromagnetic fields inside the waveguide, temperature profile, and flow pattern within the sample are investigated. The finite-difference time-domain method is used to determine the electromagnetic field distribution in a microwave cavity by solving the transient Maxwell equations. The finite control volume method based on the SIMPLE algorithm is used to predict the heat transfer and fluid flow model. Two dielectric materials, saturated porous medium and water, are chosen to display microwave heating phenomena. The simulation results agree well with the experimental data. Based on the results obtained, the inserted resonator has a strong effect on the uniformity of temperature distributions, depending on the penetration depth of microwave. The optimum distances of the resonator depend greatly on the operating frequencies. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Theoretical Analysis of Microwave Heating of dielectric materials filled in a rectangular waveguide with various resonator distances [texte imprimé] / Phadungsak Rattanadecho, Auteur ; Waraporn Klinbun, Auteur . - 2011 . - pp. [031008/1-10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031008/1-10] Mots-clés : Microwave  heating  Rectangular  waveguide  TE10  mode  Porous  medium  Resonator Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper proposes mathematical models of the microwave heating process of dielectric materials filled in a rectangular waveguide with a resonator. A microwave system supplies a monochromatic wave in a fundamental mode (TE10 mode). A convection exchange at the upper surface of the sample is considered. The effects of resonator distance and operating frequency on distributions of electromagnetic fields inside the waveguide, temperature profile, and flow pattern within the sample are investigated. The finite-difference time-domain method is used to determine the electromagnetic field distribution in a microwave cavity by solving the transient Maxwell equations. The finite control volume method based on the SIMPLE algorithm is used to predict the heat transfer and fluid flow model. Two dielectric materials, saturated porous medium and water, are chosen to display microwave heating phenomena. The simulation results agree well with the experimental data. Based on the results obtained, the inserted resonator has a strong effect on the uniformity of temperature distributions, depending on the penetration depth of microwave. The optimum distances of the resonator depend greatly on the operating frequencies. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Single-phase thermal transport of nanofluids in a minichannel / Dong Liu in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031009/1-11] Titre : Single-phase thermal transport of nanofluids in a minichannel Type de document : texte imprimé Auteurs : Dong Liu, Auteur ; Leyuan Yu, Auteur Année de publication : 2011 Article en page(s) : pp. [031009/1-11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nanofluids  Heat  transfer  Pressure  drop  Turbulence  Transition Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids have been proposed as a promising candidate for advanced heat transfer fluids in a variety of important engineering applications ranging from energy storage and electronics cooling to thermal processing of materials. In spite of the extensive studies in the literature, a consensus is lacking on if and how the dispersed nanoparticles alter the thermal transport in convective flows. In this work, an experimental investigation was conducted to study single-phase forced convection of Al2O3-water nanofluid in a circular minichannel with a 1.09 mm inner diameter. The friction factor and convection heat transfer coefficients were measured for nanofluids of various volume concentrations (up to 5%) and were compared with those of the base fluid. The Reynolds number (Re) varied from 600 to 4500, covering the laminar, transition, and early fully developed turbulent regions. It was found that in the laminar region, the nanofluids exhibit pronounced entrance region behaviors possibly due to the flattening of the velocity profile caused by the flow-induced particle migration. Three new observations were made for nanofluids in the transition and turbulent regions: (1) The onset of transition to turbulence is delayed; (2) both the friction factor and the convective heat transfer coefficient are below those of water at the same Re in the transition flow; and (3) once fully developed turbulence is established, the difference in the flow and heat transfer of nanofluids and water will diminish. A simple scaling analysis was used to show that these behaviors may be attributed to the variation in the relative size of the nanoparticle with respect to the turbulent microscales at different Re. The results from this work suggest that the particle-fluid interaction has a significant impact on the flow physics of nanofluids, especially in the transition and turbulent regions. Consequently, as a heat transfer fluid, nanofluids should be used in either the laminar flow or the fully developed turbulent flow at sufficiently high Re in order to yield enhanced heat transfer performance. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Single-phase thermal transport of nanofluids in a minichannel [texte imprimé] / Dong Liu, Auteur ; Leyuan Yu, Auteur . - 2011 . - pp. [031009/1-11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031009/1-11] Mots-clés : Nanofluids  Heat  transfer  Pressure  drop  Turbulence  Transition Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanofluids have been proposed as a promising candidate for advanced heat transfer fluids in a variety of important engineering applications ranging from energy storage and electronics cooling to thermal processing of materials. In spite of the extensive studies in the literature, a consensus is lacking on if and how the dispersed nanoparticles alter the thermal transport in convective flows. In this work, an experimental investigation was conducted to study single-phase forced convection of Al2O3-water nanofluid in a circular minichannel with a 1.09 mm inner diameter. The friction factor and convection heat transfer coefficients were measured for nanofluids of various volume concentrations (up to 5%) and were compared with those of the base fluid. The Reynolds number (Re) varied from 600 to 4500, covering the laminar, transition, and early fully developed turbulent regions. It was found that in the laminar region, the nanofluids exhibit pronounced entrance region behaviors possibly due to the flattening of the velocity profile caused by the flow-induced particle migration. Three new observations were made for nanofluids in the transition and turbulent regions: (1) The onset of transition to turbulence is delayed; (2) both the friction factor and the convective heat transfer coefficient are below those of water at the same Re in the transition flow; and (3) once fully developed turbulence is established, the difference in the flow and heat transfer of nanofluids and water will diminish. A simple scaling analysis was used to show that these behaviors may be attributed to the variation in the relative size of the nanoparticle with respect to the turbulent microscales at different Re. The results from this work suggest that the particle-fluid interaction has a significant impact on the flow physics of nanofluids, especially in the transition and turbulent regions. Consequently, as a heat transfer fluid, nanofluids should be used in either the laminar flow or the fully developed turbulent flow at sufficiently high Re in order to yield enhanced heat transfer performance. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Modeling transport in porous media with phase change / Amit Halder in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031010/1-13] Titre : Modeling transport in porous media with phase change : applications to food processing Type de document : texte imprimé Auteurs : Amit Halder, Auteur ; Ashish Dhal, Auteur ; Ashim K. Datta, Auteur Année de publication : 2011 Article en page(s) : pp. [031010/1-13] Note générale : Physique Langues : Anglais (eng) Mots-clés : Capillarity  Condensation  Convection  Diffusion  Evaporation  fats  Flow  simulation  Flow  through  porous  media  Food  manufacturing  Food  processing  industry  Mass  transfer  Melting  Porous  materials  Two-phase  flow  Water Index. décimale : 536 Chaleur. Thermodynamique Résumé : Fundamental, physics-based modeling of complex food processes is still in the developmental stages. This lack of development can be attributed to complexities in both the material and transport processes. Society has a critical need for automating food processes (both in industry and at home) while improving quality and making food safe. Product, process, and equipment designs in food manufacturing require a more detailed understanding of food processes that is possible only through physics-based modeling. The objectives of this paper are (1) to develop a general multicomponent and multiphase modeling framework that can be used for different thermal food processes and can be implemented in commercially available software (for wider use) and (2) to apply the model to the simulation of deep-fat frying and hamburger cooking processes and validate the results. Treating food material as a porous medium, heat and mass transfer inside such material during its thermal processing is described using equations for mass and energy conservation that include binary diffusion, capillary and convective modes of transport, and physicochemical changes in the solid matrix that include phase changes such as melting of fat and water and evaporation/condensation of water. Evaporation/condensation is considered to be distributed throughout the domain and is described by a novel nonequilibrium formulation whose parameters have been discussed in detail. Two complex food processes, deep-fat frying and contact heating of a hamburger patty, representing a large group of common food thermal processes with similar physics have been implemented using the modeling framework. The predictions are validated with experimental results from the literature. As the food (a porous hygroscopic material) is heated from the surface, a zone of evaporation moves from the surface to the interior. Mass transfer due to the pressure gradient (from evaporation) is significant. As temperature rises, the properties of the solid matrix change and the phases of frozen water and fat become transportable, thus affecting the transport processes significantly. Because the modeling framework is general and formulated in a manner that makes it implementable in commercial software, it can be very useful in computer-aided food manufacturing. Beyond its immediate applicability in food processing, such a comprehensive model can be useful in medicine (for thermal therapies such as laser surgery), soil remediation, nuclear waste treatment, and other fields where heat and mass transfer takes place in porous media with significant evaporation and other phase changes. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Modeling transport in porous media with phase change : applications to food processing [texte imprimé] / Amit Halder, Auteur ; Ashish Dhal, Auteur ; Ashim K. Datta, Auteur . - 2011 . - pp. [031010/1-13]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [031010/1-13] Mots-clés : Capillarity  Condensation  Convection  Diffusion  Evaporation  fats  Flow  simulation  Flow  through  porous  media  Food  manufacturing  Food  processing  industry  Mass  transfer  Melting  Porous  materials  Two-phase  flow  Water Index. décimale : 536 Chaleur. Thermodynamique Résumé : Fundamental, physics-based modeling of complex food processes is still in the developmental stages. This lack of development can be attributed to complexities in both the material and transport processes. Society has a critical need for automating food processes (both in industry and at home) while improving quality and making food safe. Product, process, and equipment designs in food manufacturing require a more detailed understanding of food processes that is possible only through physics-based modeling. The objectives of this paper are (1) to develop a general multicomponent and multiphase modeling framework that can be used for different thermal food processes and can be implemented in commercially available software (for wider use) and (2) to apply the model to the simulation of deep-fat frying and hamburger cooking processes and validate the results. Treating food material as a porous medium, heat and mass transfer inside such material during its thermal processing is described using equations for mass and energy conservation that include binary diffusion, capillary and convective modes of transport, and physicochemical changes in the solid matrix that include phase changes such as melting of fat and water and evaporation/condensation of water. Evaporation/condensation is considered to be distributed throughout the domain and is described by a novel nonequilibrium formulation whose parameters have been discussed in detail. Two complex food processes, deep-fat frying and contact heating of a hamburger patty, representing a large group of common food thermal processes with similar physics have been implemented using the modeling framework. The predictions are validated with experimental results from the literature. As the food (a porous hygroscopic material) is heated from the surface, a zone of evaporation moves from the surface to the interior. Mass transfer due to the pressure gradient (from evaporation) is significant. As temperature rises, the properties of the solid matrix change and the phases of frozen water and fat become transportable, thus affecting the transport processes significantly. Because the modeling framework is general and formulated in a manner that makes it implementable in commercial software, it can be very useful in computer-aided food manufacturing. Beyond its immediate applicability in food processing, such a comprehensive model can be useful in medicine (for thermal therapies such as laser surgery), soil remediation, nuclear waste treatment, and other fields where heat and mass transfer takes place in porous media with significant evaporation and other phase changes. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Thermal processing of tissue engineering scaffolds / Alisa Morss Clyne in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [034001/1-8] Titre : Thermal processing of tissue engineering scaffolds Type de document : texte imprimé Auteurs : Alisa Morss Clyne, Auteur Année de publication : 2011 Article en page(s) : pp. [034001/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Tissue  engineering  Scaffolds  Thermal  processing  Prosity  Fiber  bonding  Electrospinning  Emulsion  freeze  drying  Solvent  casting/particulate  leaching  Gas  foaming/particulate  leaching  High  pressure  processing  Thermally  induced  phase  separations Index. décimale : 536 Chaleur. Thermodynamique Résumé : Tissue engineering requires complex three-dimensional scaffolds that mimic natural extracellular matrix function. A wide variety of techniques have been developed to create both fibrous and porous scaffolds out of polymers, ceramics, metals, and composite materials. Existing techniques include fiber bonding, electrospinning, emulsion freeze drying, solvent casting/particulate leaching, gas foaming/particulate leaching, high pressure processing, and thermally induced phase separation. Critical scaffold properties, including pore size, porosity, pore interconnectivity, and mechanical integrity, are determined by thermal processing parameters in many of these techniques. In this review, each tissue engineering scaffold preparation method is discussed, including recent advancements as well as advantages and disadvantages of the technique, with a particular emphasis placed on thermal parameters. Improvements on these existing techniques, as well as new thermal processing methods for tissue engineering scaffolds, will be needed to provide tissue engineers with finer control over tissue and organ development. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Thermal processing of tissue engineering scaffolds [texte imprimé] / Alisa Morss Clyne, Auteur . - 2011 . - pp. [034001/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [034001/1-8] Mots-clés : Tissue  engineering  Scaffolds  Thermal  processing  Prosity  Fiber  bonding  Electrospinning  Emulsion  freeze  drying  Solvent  casting/particulate  leaching  Gas  foaming/particulate  leaching  High  pressure  processing  Thermally  induced  phase  separations Index. décimale : 536 Chaleur. Thermodynamique Résumé : Tissue engineering requires complex three-dimensional scaffolds that mimic natural extracellular matrix function. A wide variety of techniques have been developed to create both fibrous and porous scaffolds out of polymers, ceramics, metals, and composite materials. Existing techniques include fiber bonding, electrospinning, emulsion freeze drying, solvent casting/particulate leaching, gas foaming/particulate leaching, high pressure processing, and thermally induced phase separation. Critical scaffold properties, including pore size, porosity, pore interconnectivity, and mechanical integrity, are determined by thermal processing parameters in many of these techniques. In this review, each tissue engineering scaffold preparation method is discussed, including recent advancements as well as advantages and disadvantages of the technique, with a particular emphasis placed on thermal parameters. Improvements on these existing techniques, as well as new thermal processing methods for tissue engineering scaffolds, will be needed to provide tissue engineers with finer control over tissue and organ development. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

Titania nanotubes / Nathan Swami in Journal of heat transfer, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [034002/1-7] Titre : Titania nanotubes : novel nanostructures for improved osseointegration Type de document : texte imprimé Auteurs : Nathan Swami, Auteur ; Zhanwu Cui, Auteur ; Lakshmi S. Nair, Auteur Année de publication : 2011 Article en page(s) : pp. [034002/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Titania  nanotube  Osseointegration  Electrochemical  synthesis  Wet  chemical  synthesis Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanostructured one dimensional titanium oxides such as nanotubes and nanowires have raised interest lately due to their unique electronic and optical properties. These materials also have shown significant potential as biomaterials because of their ability to modulate protein and cellular interactions. In this review, synthesis and modification of titania nanotubes have been discussed with emphasis on electrochemical synthesis and wet chemical synthesis and their heat treatment of resulting titania nanotubes. The biomedical applications of titania nanotubes were subsequently discussed in detail with a focus on osseointegration. The areas discussed are cell responses to titania nanotubes, effects of titania nanotubes on stem cell proliferation and differentiation, titania nanotubes as drug delivery vehicles, surface modification of titania nanotubes, and in vivo studies using titania nanotubes. It is concluded that the in vitro and in vivo study clearly demonstrates the efficacy of titania nanotube in enhancing osseointegration of orthopedic implants and much of the future work is expected to focus on improving implant functions by modulating the physical and chemical properties of the nanotubes and by locally delivering bioactive molecules in a sustained manner. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Titania nanotubes : novel nanostructures for improved osseointegration [texte imprimé] / Nathan Swami, Auteur ; Zhanwu Cui, Auteur ; Lakshmi S. Nair, Auteur . - 2011 . - pp. [034002/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 3 (Mars 2011) . - pp. [034002/1-7] Mots-clés : Titania  nanotube  Osseointegration  Electrochemical  synthesis  Wet  chemical  synthesis Index. décimale : 536 Chaleur. Thermodynamique Résumé : Nanostructured one dimensional titanium oxides such as nanotubes and nanowires have raised interest lately due to their unique electronic and optical properties. These materials also have shown significant potential as biomaterials because of their ability to modulate protein and cellular interactions. In this review, synthesis and modification of titania nanotubes have been discussed with emphasis on electrochemical synthesis and wet chemical synthesis and their heat treatment of resulting titania nanotubes. The biomedical applications of titania nanotubes were subsequently discussed in detail with a focus on osseointegration. The areas discussed are cell responses to titania nanotubes, effects of titania nanotubes on stem cell proliferation and differentiation, titania nanotubes as drug delivery vehicles, surface modification of titania nanotubes, and in vivo studies using titania nanotubes. It is concluded that the in vitro and in vivo study clearly demonstrates the efficacy of titania nanotube in enhancing osseointegration of orthopedic implants and much of the future work is expected to focus on improving implant functions by modulating the physical and chemical properties of the nanotubes and by locally delivering bioactive molecules in a sustained manner. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]

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