Dépouillements

Effects of axial corrugated roughness on low Reynolds number slip flow and continuum flow in microtubes / Zhipeng Duan in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041001-1/9] Titre : Effects of axial corrugated roughness on low Reynolds number slip flow and continuum flow in microtubes Type de document : texte imprimé Auteurs : Zhipeng Duan, Auteur ; Y. S. Muzychka, Auteur Article en page(s) : pp. [041001-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Corrugations  Roughness  Perturbation  Slip  flow  Microtubes Index. décimale : 536 Chaleur. Thermodynamique Résumé : The effect of axial corrugated surface roughness on fully developed laminar flow in microtubes is investigated. The radius of a microtube varies with the axial distance due to corrugated roughness. The Stokes equation is solved using a perturbation method with slip at the boundary. Analytical models are developed to predict friction factor and pressure drop in corrugated rough microtubes for continuum flow and slip flow. The developed model proposes an explanation on the observed phenomenon that some experimental pressure drop results for microchannel flow have shown a significant increase due to roughness. The developed model for slip flow illustrates the coupled effects between velocity slip and small corrugated roughness. Compressibility effect has also been examined and simple models are proposed to predict the pressure distribution and mass flow rate for slip flow in corrugated rough microtubes. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Effects of axial corrugated roughness on low Reynolds number slip flow and continuum flow in microtubes [texte imprimé] / Zhipeng Duan, Auteur ; Y. S. Muzychka, Auteur . - pp. [041001-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041001-1/9] Mots-clés : Corrugations  Roughness  Perturbation  Slip  flow  Microtubes Index. décimale : 536 Chaleur. Thermodynamique Résumé : The effect of axial corrugated surface roughness on fully developed laminar flow in microtubes is investigated. The radius of a microtube varies with the axial distance due to corrugated roughness. The Stokes equation is solved using a perturbation method with slip at the boundary. Analytical models are developed to predict friction factor and pressure drop in corrugated rough microtubes for continuum flow and slip flow. The developed model proposes an explanation on the observed phenomenon that some experimental pressure drop results for microchannel flow have shown a significant increase due to roughness. The developed model for slip flow illustrates the coupled effects between velocity slip and small corrugated roughness. Compressibility effect has also been examined and simple models are proposed to predict the pressure distribution and mass flow rate for slip flow in corrugated rough microtubes. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Flow boiling on micropin fins entrenched inside a microchannel—flow patterns and bubble departure diameter and bubble frequency / Santosh Krishnamurthy in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041002-1/9] Titre : Flow boiling on micropin fins entrenched inside a microchannel—flow patterns and bubble departure diameter and bubble frequency Type de document : texte imprimé Auteurs : Santosh Krishnamurthy, Auteur ; Yoav Peles, Auteur Article en page(s) : pp. [041002-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Flow  boiling  Microchannel  Micro-pin  fin  Bubble  departure  frequency  Bubble  departure  diameter  Surface  tension Index. décimale : 536 Chaleur. Thermodynamique Résumé : Flow boiling of HFE 7000 in five parallel microchannels of 222 µm hydraulic diameter, each containing a single row of 24 in-line 100 µm pin fins, was investigated. High speed photography revealed the dominant flow patterns, namely, the bubbly flow, the multiple flow, and the wavy-annular flow. The interaction of the bubble with the pin fins during nucleate boiling from G=350 kg/m2 s to G=827 kg/m2 s and wall heat fluxes from 10 W/cm2 to 110 W/cm2 is detailed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Flow boiling on micropin fins entrenched inside a microchannel—flow patterns and bubble departure diameter and bubble frequency [texte imprimé] / Santosh Krishnamurthy, Auteur ; Yoav Peles, Auteur . - pp. [041002-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041002-1/9] Mots-clés : Flow  boiling  Microchannel  Micro-pin  fin  Bubble  departure  frequency  Bubble  departure  diameter  Surface  tension Index. décimale : 536 Chaleur. Thermodynamique Résumé : Flow boiling of HFE 7000 in five parallel microchannels of 222 µm hydraulic diameter, each containing a single row of 24 in-line 100 µm pin fins, was investigated. High speed photography revealed the dominant flow patterns, namely, the bubbly flow, the multiple flow, and the wavy-annular flow. The interaction of the bubble with the pin fins during nucleate boiling from G=350 kg/m2 s to G=827 kg/m2 s and wall heat fluxes from 10 W/cm2 to 110 W/cm2 is detailed. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Heat transfer in microchannels with suspended solid particles / Reza H. Khiabani in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041003-1/9] Titre : Heat transfer in microchannels with suspended solid particles : lattice-boltzmann based computations Type de document : texte imprimé Auteurs : Reza H. Khiabani, Auteur ; Yogendra Joshi, Auteur ; Cyrus K. Aidun, Auteur Article en page(s) : pp. [041003-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Nanofluid  heat  transfer  Suspended  particles  Lattice-Boltzmann  method  for  heat  transfer  Numerical  simulation Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper presents computational results on the effect of fixed or suspended cylindrical solid particles on heat transfer in a channel flow. The computational method is based on the solution of the lattice-Boltzmann equation for the fluid flow, coupled with the energy equation for thermal transport and the Newtonian dynamic equations for direct simulation of suspended particle transport. The effects of Reynolds number, particle-to-channel size ratio, and the eccentricity of the particle on heat transfer from the channel walls for single and multi-particles are presented. The multi-particle flow condition represents a case with solid particles suspended in the cooling medium, such as in micro/nanofluids, to augment heat transfer. The results provide insight into the mechanism by which suspended particles can change the rate of heat transfer in a microchannel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Heat transfer in microchannels with suspended solid particles : lattice-boltzmann based computations [texte imprimé] / Reza H. Khiabani, Auteur ; Yogendra Joshi, Auteur ; Cyrus K. Aidun, Auteur . - pp. [041003-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041003-1/9] Mots-clés : Nanofluid  heat  transfer  Suspended  particles  Lattice-Boltzmann  method  for  heat  transfer  Numerical  simulation Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper presents computational results on the effect of fixed or suspended cylindrical solid particles on heat transfer in a channel flow. The computational method is based on the solution of the lattice-Boltzmann equation for the fluid flow, coupled with the energy equation for thermal transport and the Newtonian dynamic equations for direct simulation of suspended particle transport. The effects of Reynolds number, particle-to-channel size ratio, and the eccentricity of the particle on heat transfer from the channel walls for single and multi-particles are presented. The multi-particle flow condition represents a case with solid particles suspended in the cooling medium, such as in micro/nanofluids, to augment heat transfer. The results provide insight into the mechanism by which suspended particles can change the rate of heat transfer in a microchannel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Generalized two-phase pressure drop and heat transfer correlations in evaporative micro/minichannels / Hee Joon Lee in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041004-1/9] Titre : Generalized two-phase pressure drop and heat transfer correlations in evaporative micro/minichannels Type de document : texte imprimé Auteurs : Hee Joon Lee, Auteur ; Dong Yao Liu, Auteur ; Y. Alyousef, Auteur Article en page(s) : pp. [041004-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Two-phase  Correlation  Pressure  drop  heat  transfer  Evaporation  Microchannel Index. décimale : 536 Chaleur. Thermodynamique Résumé : Existing databases and correlations in literature on the microchannel pressure drop and heat transfer are reviewed in this paper. From this review, it is found that none of the existing correlations can cover the wide ranges of working fluids, operational conditions, and different microchannel dimensions. In addition, the importance of the Bond number, which relates the nominal bubble dimension or capillary parameter with the channel size, is revealed in this paper. Using the Bond number, improved correlations of pressure drop and heat transfer are established, which predict the existing data well over a wide range of channel sizes, fluids, and operational conditions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Generalized two-phase pressure drop and heat transfer correlations in evaporative micro/minichannels [texte imprimé] / Hee Joon Lee, Auteur ; Dong Yao Liu, Auteur ; Y. Alyousef, Auteur . - pp. [041004-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041004-1/9] Mots-clés : Two-phase  Correlation  Pressure  drop  heat  transfer  Evaporation  Microchannel Index. décimale : 536 Chaleur. Thermodynamique Résumé : Existing databases and correlations in literature on the microchannel pressure drop and heat transfer are reviewed in this paper. From this review, it is found that none of the existing correlations can cover the wide ranges of working fluids, operational conditions, and different microchannel dimensions. In addition, the importance of the Bond number, which relates the nominal bubble dimension or capillary parameter with the channel size, is revealed in this paper. Using the Bond number, improved correlations of pressure drop and heat transfer are established, which predict the existing data well over a wide range of channel sizes, fluids, and operational conditions. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Numerical investigation of heat transfer enhancement in a microchannel with grooved surfaces / O. Abouali in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041005-1/8] Titre : Numerical investigation of heat transfer enhancement in a microchannel with grooved surfaces Type de document : texte imprimé Auteurs : O. Abouali, Auteur ; N. Baghernezhad, Auteur Article en page(s) : pp. [041005-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microchannel  Groove  Heat  transfer  enhancement  COP Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper presents a numerical investigation for two types of grooves (rectangular and arc shapes) fabricated in the microchannel surfaces, which leads to enhancement in single-phase cooling. The pressure drop and heat transfer characteristics of the single-phase microchannel heat sink were investigated numerically for laminar flow. For this purpose, the conjugate heat transfer problem involving simultaneous determination of temperature fields in both solid and liquid regions was solved numerically. The numerical model was validated with comparison to experimental data, in which good agreement was seen. A simple microchannel with available experimental data was selected, and it was shown that using grooved surfaces on this microchannel has a noticeable effect and heat removal rate can be increased using this technique. The results depict that the arc grooves have a higher heat removal flux compared with rectangular grooves but the latter have a higher coefficient of performance for the case in which grooves are made in the floor and both side walls. Also, it was shown that a grooved microchannel with higher wall thickness and lower mass flow rate of cooling water has a higher heat removal flux and coefficient of performance compared with a simple microchannel with minimum wall thickness. Effect of various sizes and distances of the floor grooves was determined, and the cases for maximum heat removal rate and coefficient of performance for both rectangular and arc grooves were obtained. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Numerical investigation of heat transfer enhancement in a microchannel with grooved surfaces [texte imprimé] / O. Abouali, Auteur ; N. Baghernezhad, Auteur . - pp. [041005-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041005-1/8] Mots-clés : Microchannel  Groove  Heat  transfer  enhancement  COP Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper presents a numerical investigation for two types of grooves (rectangular and arc shapes) fabricated in the microchannel surfaces, which leads to enhancement in single-phase cooling. The pressure drop and heat transfer characteristics of the single-phase microchannel heat sink were investigated numerically for laminar flow. For this purpose, the conjugate heat transfer problem involving simultaneous determination of temperature fields in both solid and liquid regions was solved numerically. The numerical model was validated with comparison to experimental data, in which good agreement was seen. A simple microchannel with available experimental data was selected, and it was shown that using grooved surfaces on this microchannel has a noticeable effect and heat removal rate can be increased using this technique. The results depict that the arc grooves have a higher heat removal flux compared with rectangular grooves but the latter have a higher coefficient of performance for the case in which grooves are made in the floor and both side walls. Also, it was shown that a grooved microchannel with higher wall thickness and lower mass flow rate of cooling water has a higher heat removal flux and coefficient of performance compared with a simple microchannel with minimum wall thickness. Effect of various sizes and distances of the floor grooves was determined, and the cases for maximum heat removal rate and coefficient of performance for both rectangular and arc grooves were obtained. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

An extension to the Navier–Stokes equations to incorporate gas molecular collisions with boundaries / Erik J. Arlemark in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041006-1/8] Titre : An extension to the Navier–Stokes equations to incorporate gas molecular collisions with boundaries Type de document : texte imprimé Auteurs : Erik J. Arlemark, Auteur ; S. Kokou Dadzie, Auteur ; Jason M. Reese, Auteur Article en page(s) : pp. [041006-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microgas-flow  Navier-Stokes  equations  Mean-free-path  Nonlinear  constitutive  relationships  Velocity-slip  Knudsen-layer Index. décimale : 536 Chaleur. Thermodynamique Résumé : We investigate a model for microgas-flows consisting of the Navier–Stokes equations extended to include a description of molecular collisions with solid-boundaries together with first- and second-order velocity-slip boundary conditions. By considering molecular collisions affected by boundaries in gas flows, we capture some of the near-wall effects that the conventional Navier–Stokes equations with a linear stress-/strain-rate relationship are unable to describe. Our model is expressed through a geometry-dependent mean-free-path yielding a new viscosity expression, which makes the stress-/strain-rate constitutive relationship nonlinear. Test cases consisting of Couette and Poiseuille flows are solved using these extended Navier–Stokes equations and we compare the resulting velocity profiles with conventional Navier–Stokes solutions and those from the BGK kinetic model. The Poiseuille mass flow rate results are compared with results from the BGK-model and experimental data for various degrees of rarefaction. We assess the range of applicability of our model and show that it can extend the applicability of conventional fluid dynamic techniques into the early continuum-transition regime. We also discuss the limitations of our model due to its various physical assumptions and we outline ideas for further development. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] An extension to the Navier–Stokes equations to incorporate gas molecular collisions with boundaries [texte imprimé] / Erik J. Arlemark, Auteur ; S. Kokou Dadzie, Auteur ; Jason M. Reese, Auteur . - pp. [041006-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041006-1/8] Mots-clés : Microgas-flow  Navier-Stokes  equations  Mean-free-path  Nonlinear  constitutive  relationships  Velocity-slip  Knudsen-layer Index. décimale : 536 Chaleur. Thermodynamique Résumé : We investigate a model for microgas-flows consisting of the Navier–Stokes equations extended to include a description of molecular collisions with solid-boundaries together with first- and second-order velocity-slip boundary conditions. By considering molecular collisions affected by boundaries in gas flows, we capture some of the near-wall effects that the conventional Navier–Stokes equations with a linear stress-/strain-rate relationship are unable to describe. Our model is expressed through a geometry-dependent mean-free-path yielding a new viscosity expression, which makes the stress-/strain-rate constitutive relationship nonlinear. Test cases consisting of Couette and Poiseuille flows are solved using these extended Navier–Stokes equations and we compare the resulting velocity profiles with conventional Navier–Stokes solutions and those from the BGK kinetic model. The Poiseuille mass flow rate results are compared with results from the BGK-model and experimental data for various degrees of rarefaction. We assess the range of applicability of our model and show that it can extend the applicability of conventional fluid dynamic techniques into the early continuum-transition regime. We also discuss the limitations of our model due to its various physical assumptions and we outline ideas for further development. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Flow boiling heat transfer on micro pin fins entrenched in a microchannel / Santosh Krishnamurthy in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041007-1/10] Titre : Flow boiling heat transfer on micro pin fins entrenched in a microchannel Type de document : texte imprimé Auteurs : Santosh Krishnamurthy, Auteur ; Yoav Peles, Auteur Article en page(s) : pp. [041007-1/10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Micro  pin  fins  Heat  transfer  coefficient  Flow  maps Index. décimale : 536 Chaleur. Thermodynamique Résumé : Flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in 222 µm hydraulic diameter channels containing a single row of 24 inline 100 µm pin fins was studied for mass fluxes from 350 kg/m2 s to 827 kg/m2 s and wall heat fluxes from 10 W/cm2 to 110 W/cm2. Flow visualization revealed the existence of isolated bubbles, bubbles interacting, multiple flow, and annular flow. The observed flow patterns were mapped as a function of the boiling number and the normalized axial distance. The local heat transfer coefficient during subcooled boiling was measured and found to be considerably higher than the corresponding single-phase flow. Furthermore, a thermal performance evaluation comparison with a plain microchannel revealed that the presence of pin fins considerably enhanced the heat transfer coefficient. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Flow boiling heat transfer on micro pin fins entrenched in a microchannel [texte imprimé] / Santosh Krishnamurthy, Auteur ; Yoav Peles, Auteur . - pp. [041007-1/10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041007-1/10] Mots-clés : Micro  pin  fins  Heat  transfer  coefficient  Flow  maps Index. décimale : 536 Chaleur. Thermodynamique Résumé : Flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in 222 µm hydraulic diameter channels containing a single row of 24 inline 100 µm pin fins was studied for mass fluxes from 350 kg/m2 s to 827 kg/m2 s and wall heat fluxes from 10 W/cm2 to 110 W/cm2. Flow visualization revealed the existence of isolated bubbles, bubbles interacting, multiple flow, and annular flow. The observed flow patterns were mapped as a function of the boiling number and the normalized axial distance. The local heat transfer coefficient during subcooled boiling was measured and found to be considerably higher than the corresponding single-phase flow. Furthermore, a thermal performance evaluation comparison with a plain microchannel revealed that the presence of pin fins considerably enhanced the heat transfer coefficient. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Using direct simulation Monte Carlo with improved boundary conditions for heat and mass transfer in microchannels / J. Yang in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041008-1/9] Titre : Using direct simulation Monte Carlo with improved boundary conditions for heat and mass transfer in microchannels Type de document : texte imprimé Auteurs : J. Yang, Auteur ; J. J. Ye, Auteur ; J. Y. Zheng, Auteur Article en page(s) : pp. [041008-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Direct  simulation  Monte  Carlo  Heat  flux  Mass  flowrate  Microfluidics  Pressure  boundary  conditions Index. décimale : 536 Chaleur. Thermodynamique Résumé : Micro-electromechanical systems and nano-electromechanical systems have attracted a great deal of attention in recent years. The flow and heat transfer behaviors of micromachines for separation applications are usually different from that of macro counterparts. In this paper, heat and mass transfer characteristics of rarefied nitrogen gas flows in microchannels are investigated using direct simulation Monte Carlo with improved pressure boundary conditions. The influence of aspect ratio and wall temperature on mass flowrate and wall heat flux in microchannels are studied parametrically. In order to examine the aspect ratio effect on heat and mass transfer behaviors, the wall temperature is set constant at 350 K and the aspect ratio of the microchannel varies from 5 to 20. The results show that as the aspect ratio increases, the velocity of the flow decreases, so does the mass flowrate. In a small aspect ratio channel, the heat transfer occurs throughout the microchannel; as the aspect ratio of the microchannel increases, the region of thermal equilibrium extends. To investigate the effects of wall temperature (Tw) on the mass flowrate and wall heat flux in a microchannel, the temperature of the incoming gas flow (Tin) is set constant at 300 K and the wall temperature varies from 200 K to 800 K while the aspect ratio is remained unchanged. Results show that majority of the wall heat flux stays within the channel entrance region and drops to nearly zero at the halfway in the channel. When TwTin, the molecular number density of the flow drops rapidly near the inlet and the temperature of the gas flow increases along the channel. As Tw increases, the flow becomes more rarefied, the mass flowrate decreases, and the resistance at the entrance region increases. Furthermore, when Tw>Tin, a sudden jump of heat transfer flux and temperature are observed at the exit region of the channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Using direct simulation Monte Carlo with improved boundary conditions for heat and mass transfer in microchannels [texte imprimé] / J. Yang, Auteur ; J. J. Ye, Auteur ; J. Y. Zheng, Auteur . - pp. [041008-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041008-1/9] Mots-clés : Direct  simulation  Monte  Carlo  Heat  flux  Mass  flowrate  Microfluidics  Pressure  boundary  conditions Index. décimale : 536 Chaleur. Thermodynamique Résumé : Micro-electromechanical systems and nano-electromechanical systems have attracted a great deal of attention in recent years. The flow and heat transfer behaviors of micromachines for separation applications are usually different from that of macro counterparts. In this paper, heat and mass transfer characteristics of rarefied nitrogen gas flows in microchannels are investigated using direct simulation Monte Carlo with improved pressure boundary conditions. The influence of aspect ratio and wall temperature on mass flowrate and wall heat flux in microchannels are studied parametrically. In order to examine the aspect ratio effect on heat and mass transfer behaviors, the wall temperature is set constant at 350 K and the aspect ratio of the microchannel varies from 5 to 20. The results show that as the aspect ratio increases, the velocity of the flow decreases, so does the mass flowrate. In a small aspect ratio channel, the heat transfer occurs throughout the microchannel; as the aspect ratio of the microchannel increases, the region of thermal equilibrium extends. To investigate the effects of wall temperature (Tw) on the mass flowrate and wall heat flux in a microchannel, the temperature of the incoming gas flow (Tin) is set constant at 300 K and the wall temperature varies from 200 K to 800 K while the aspect ratio is remained unchanged. Results show that majority of the wall heat flux stays within the channel entrance region and drops to nearly zero at the halfway in the channel. When TwTin, the molecular number density of the flow drops rapidly near the inlet and the temperature of the gas flow increases along the channel. As Tw increases, the flow becomes more rarefied, the mass flowrate decreases, and the resistance at the entrance region increases. Furthermore, when Tw>Tin, a sudden jump of heat transfer flux and temperature are observed at the exit region of the channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Thermal characterization of interlayer microfluidic cooling of three-dimensional integrated circuits with nonuniform heat flux / Yoon Jo Kim in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041009-1/9] Titre : Thermal characterization of interlayer microfluidic cooling of three-dimensional integrated circuits with nonuniform heat flux Type de document : texte imprimé Auteurs : Yoon Jo Kim, Auteur ; Yogendra K. Joshi, Auteur ; Andrei G. Fedorov, Auteur Article en page(s) : pp. [041009-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microchannel  Microfluidic  cooling  Three-dimensional  IC  Nonuniform  heat  flux  Single-phase  Two-phase  Pressure  drop Index. décimale : 536 Chaleur. Thermodynamique Résumé : It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ~300 W/cm2. In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Thermal characterization of interlayer microfluidic cooling of three-dimensional integrated circuits with nonuniform heat flux [texte imprimé] / Yoon Jo Kim, Auteur ; Yogendra K. Joshi, Auteur ; Andrei G. Fedorov, Auteur . - pp. [041009-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041009-1/9] Mots-clés : Microchannel  Microfluidic  cooling  Three-dimensional  IC  Nonuniform  heat  flux  Single-phase  Two-phase  Pressure  drop Index. décimale : 536 Chaleur. Thermodynamique Résumé : It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ~300 W/cm2. In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Representative results for condensation measurements at hydraulic diameters ~100 microns / Akhil Agarwal in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041010-1/12] Titre : Representative results for condensation measurements at hydraulic diameters ~100 microns Type de document : texte imprimé Auteurs : Akhil Agarwal, Auteur ; Srinivas Garimella, Auteur Article en page(s) : pp. [041010-1/12] Note générale : Physique Langues : Anglais (eng) Mots-clés : Condensation  Microchannels  Measurement  Heat  transfer  Pressure  drop  refrigerants Index. décimale : 536 Chaleur. Thermodynamique Résumé : Condensation pressure drops and heat transfer coefficients for refrigerant R134a flowing through rectangular microchannels with hydraulic diameters ranging from 100 µm to 200 µm are measured in small quality increments. The channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the preheaters and postheaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test-section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for mass fluxes ranging from 200 kg/m2 s to 800 kg/m2 s for 0< quality <1 at several different saturation temperatures. Conjugate heat transfer analyses are conducted in conjunction with local pressure drop profiles to obtain accurate driving temperature differences and heat transfer coefficients. The effects of quality, mass flux, and saturation temperature on condensation pressure drops and heat transfer coefficients are illustrated through these experiments. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Representative results for condensation measurements at hydraulic diameters ~100 microns [texte imprimé] / Akhil Agarwal, Auteur ; Srinivas Garimella, Auteur . - pp. [041010-1/12]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041010-1/12] Mots-clés : Condensation  Microchannels  Measurement  Heat  transfer  Pressure  drop  refrigerants Index. décimale : 536 Chaleur. Thermodynamique Résumé : Condensation pressure drops and heat transfer coefficients for refrigerant R134a flowing through rectangular microchannels with hydraulic diameters ranging from 100 µm to 200 µm are measured in small quality increments. The channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the preheaters and postheaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test-section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for mass fluxes ranging from 200 kg/m2 s to 800 kg/m2 s for 0< quality <1 at several different saturation temperatures. Conjugate heat transfer analyses are conducted in conjunction with local pressure drop profiles to obtain accurate driving temperature differences and heat transfer coefficients. The effects of quality, mass flux, and saturation temperature on condensation pressure drops and heat transfer coefficients are illustrated through these experiments. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Investigation into the similarity solution for boundary layer flows in microsystems / Suhil Kiwan in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041011-1/9] Titre : Investigation into the similarity solution for boundary layer flows in microsystems Type de document : texte imprimé Auteurs : Suhil Kiwan, Auteur ; M. A. Al-Nimr, Auteur Article en page(s) : pp. [041011-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Similarity  solution  Stagnation  surface  Rarafied  gaz  Velocity  slip  parameter  Temperature  jump  parameter Index. décimale : 536 Chaleur. Thermodynamique Résumé : An investigation toward the existence of a complete similarity solution for boundary layer flows under the velocity slip and temperature jump conditions is carried out. The study is limited to the boundary layer flows resulting from an arbitrary freestream velocity U(x)=Uoxm and wall temperature given by Tw−T[infinity]=Cxn. It is found that a similar solution exists only for m=1 and n=0, which represents stagnation flow on isothermal surface. This case has been thoroughly investigated. The analysis showed that three parameters control the flow and heat transfer characteristics of the problem. These parameters are the velocity slip parameter K1, the temperature jump parameter K2, and Prandtl number. The effect of these parameters on the flow and heat transfer of the problem has been studied and presented. It is found that the slip velocity parameter affects both the flow and heat transfer characteristics of the problem. It is found that the skin friction coefficient decreases with increasing K1 and most of changes in the skin friction takes place in the range 0x-0.5(K1+1.279)−0.8 for 011.06)/(0.515+K11.06)](K2+1.489Pr−0.44)−1, for 0 DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Investigation into the similarity solution for boundary layer flows in microsystems [texte imprimé] / Suhil Kiwan, Auteur ; M. A. Al-Nimr, Auteur . - pp. [041011-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041011-1/9] Mots-clés : Similarity  solution  Stagnation  surface  Rarafied  gaz  Velocity  slip  parameter  Temperature  jump  parameter Index. décimale : 536 Chaleur. Thermodynamique Résumé : An investigation toward the existence of a complete similarity solution for boundary layer flows under the velocity slip and temperature jump conditions is carried out. The study is limited to the boundary layer flows resulting from an arbitrary freestream velocity U(x)=Uoxm and wall temperature given by Tw−T[infinity]=Cxn. It is found that a similar solution exists only for m=1 and n=0, which represents stagnation flow on isothermal surface. This case has been thoroughly investigated. The analysis showed that three parameters control the flow and heat transfer characteristics of the problem. These parameters are the velocity slip parameter K1, the temperature jump parameter K2, and Prandtl number. The effect of these parameters on the flow and heat transfer of the problem has been studied and presented. It is found that the slip velocity parameter affects both the flow and heat transfer characteristics of the problem. It is found that the skin friction coefficient decreases with increasing K1 and most of changes in the skin friction takes place in the range 0x-0.5(K1+1.279)−0.8 for 011.06)/(0.515+K11.06)](K2+1.489Pr−0.44)−1, for 0 DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Analytical modeling of annular flow boiling heat transfer in mini- and microchannel heat sinks / A. Megahed in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041012-1/11] Titre : Analytical modeling of annular flow boiling heat transfer in mini- and microchannel heat sinks Type de document : texte imprimé Auteurs : A. Megahed, Auteur ; I. Hassan, Auteur Article en page(s) : pp. [041012-1/11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Annular  flow  Two-phase  flow  Two-phase  heat  transfer  coefficient  Mini  and  microchannel  heat  sinks Index. décimale : 536 Chaleur. Thermodynamique Résumé : An analytical model is proposed to predict the flow boiling heat transfer coefficient in the annular flow regime in mini- and microchannel heat sinks based on the separated model. The modeling procedure includes a formulation for determining the heat transfer coefficient based on the wall shear stress and the local thermophysical characteristics of the fluid based on the Reynolds' analogy. The frictional and acceleration pressure gradients within the channel are incorporated into the present model to provide a better representation of the flow conditions. The model is validated against collected data sets from the literature produced by different authors under different experimental conditions, different fluids, and with mini- and microchannels of hydraulic diameters falling within the range of 92–1440 µm. The accuracy between the experimental and predicted results is achieved with a mean absolute error of 10%. The present analytical model can correctly predict the different trends of the heat transfer coefficient reported in the literature as a function of the exit quality. The predicted two-phase heat transfer coefficient is found to be very sensitive to changes in mass flux and saturation temperature. However, it is found to be mildly sensitive to the change in heat flux. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Analytical modeling of annular flow boiling heat transfer in mini- and microchannel heat sinks [texte imprimé] / A. Megahed, Auteur ; I. Hassan, Auteur . - pp. [041012-1/11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041012-1/11] Mots-clés : Annular  flow  Two-phase  flow  Two-phase  heat  transfer  coefficient  Mini  and  microchannel  heat  sinks Index. décimale : 536 Chaleur. Thermodynamique Résumé : An analytical model is proposed to predict the flow boiling heat transfer coefficient in the annular flow regime in mini- and microchannel heat sinks based on the separated model. The modeling procedure includes a formulation for determining the heat transfer coefficient based on the wall shear stress and the local thermophysical characteristics of the fluid based on the Reynolds' analogy. The frictional and acceleration pressure gradients within the channel are incorporated into the present model to provide a better representation of the flow conditions. The model is validated against collected data sets from the literature produced by different authors under different experimental conditions, different fluids, and with mini- and microchannels of hydraulic diameters falling within the range of 92–1440 µm. The accuracy between the experimental and predicted results is achieved with a mean absolute error of 10%. The present analytical model can correctly predict the different trends of the heat transfer coefficient reported in the literature as a function of the exit quality. The predicted two-phase heat transfer coefficient is found to be very sensitive to changes in mass flux and saturation temperature. However, it is found to be mildly sensitive to the change in heat flux. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Experimental investigation of single-phase microjet array heat transfer / Eric A. Browne in Journal of heat transfer, Vol. 132 N° 4 (n° spécial) (Avril 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041013-1/9] Titre : Experimental investigation of single-phase microjet array heat transfer Type de document : texte imprimé Auteurs : Eric A. Browne, Auteur ; Gregory J. Michna, Auteur ; Michael K. Jensen, Auteur Article en page(s) : pp. [041013-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Electronics  cooling  Microscale  jet  heat  transfer  Microjet  Microjet  array Index. décimale : 536 Chaleur. Thermodynamique Résumé : The heat transfer performance of two microjet arrays was investigated using degassed deionized water and air. The inline jet arrays had diameters of 54 µm and 112 µm, a spacing of 250 µm, a standoff of 200 µm (S/d=2.2 and 4.6, H/d=1.8 and 3.7), and jet-to-heater area ratios from 0.036 to 0.16. Average heat transfer coefficients with deionized water were obtained for 150<=Red<=3300 and ranged from 80,000 W/m2 K to 414,000 W/m2 K. A heat flux of 1110 W/cm2 was attained with 23°C inlet water and an average surface temperature of 50°C. The Reynolds number range for the same arrays with air was 300<=Red<=4900 with average heat transfer coefficients of 2500 W/m2 K to 15,000 W/m2 K. The effect of the Mach number on the area-averaged Nusselt number was found to be negligible. The data were compared with available correlations for submerged jet array heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Experimental investigation of single-phase microjet array heat transfer [texte imprimé] / Eric A. Browne, Auteur ; Gregory J. Michna, Auteur ; Michael K. Jensen, Auteur . - pp. [041013-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 4 (n° spécial) (Avril 2010) . - pp. [041013-1/9] Mots-clés : Electronics  cooling  Microscale  jet  heat  transfer  Microjet  Microjet  array Index. décimale : 536 Chaleur. Thermodynamique Résumé : The heat transfer performance of two microjet arrays was investigated using degassed deionized water and air. The inline jet arrays had diameters of 54 µm and 112 µm, a spacing of 250 µm, a standoff of 200 µm (S/d=2.2 and 4.6, H/d=1.8 and 3.7), and jet-to-heater area ratios from 0.036 to 0.16. Average heat transfer coefficients with deionized water were obtained for 150<=Red<=3300 and ranged from 80,000 W/m2 K to 414,000 W/m2 K. A heat flux of 1110 W/cm2 was attained with 23°C inlet water and an average surface temperature of 50°C. The Reynolds number range for the same arrays with air was 300<=Red<=4900 with average heat transfer coefficients of 2500 W/m2 K to 15,000 W/m2 K. The effect of the Mach number on the area-averaged Nusselt number was found to be negligible. The data were compared with available correlations for submerged jet array heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

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